190 results on '"Hiroki Akutsu"'
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2. A 2D Interactive Spin Ladder System, δ′-(BEDT-TTF)2ClC2H4SO3·H2O
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Hiroki Akutsu, Scott S. Turner, and Yasuhiro Nakazawa
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General Materials Science ,General Chemistry ,Condensed Matter Physics - Published
- 2022
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3. Magnetic field induced transition in the charge-glass former θ−(BEDT−TTF)2CsCo(SCN)4
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Tetsuya Nomoto, Satoshi Yamashita, Hiroki Akutsu, and Yasuhiro Nakazawa
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- 2023
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4. Thermodynamic Properties of the Mott Insulator-Metal Transition in a Triangular Lattice System Without Magnetic Order
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Emre Yesil, Shusaku Imajo, Satoshi Yamashita, Hiroki Akutsu, Yohei Saito, Andrej Pustogow, Atsushi Kawamoto, and Yasuhiro Nakazawa
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Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Materials Science ,Strongly Correlated Electrons (cond-mat.str-el) ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences - Abstract
The organic system, $\kappa$-[(BEDT-TTF)$_{1-x}$(BEDT-STF)$_x$]$_2$Cu$_2$(CN)$_3$, showing the Mott transition between a nonmagnetic Mott insulating (NMI) state and a Fermi liquid (FL), is systematically studied by calorimetric measurements. An increase of the electronic heat capacity at the transition from the NMI state to the FL state which keeps the triangular dimer lattice demonstrates that the charge sector lost in the Mott insulating state is recovered in the FL state. We observed that the remaining low-energy spin excitations in the Mott insulating state show unique temperature dependence, and that the NMI state has a larger lattice entropy originating from the frustrated lattice, which leads to the Pomeranchuk-like effect on the electron localization. Near the Mott boundary, an unexpected enhancement and magnetic-field dependence of heat capacity are observed. This anomalous heat capacity is different from the behavior in the typical first-order Mott transition and shows similarities with quantum critical behavior. To reconcile our results with previously reported scenarios about a spin gap and the first-order Mott transition, further studies are desired., Comment: 9 pages, 4 figures
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- 2023
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5. Thermal conductivity measurement system for molecules-based compounds available in a wide temperature region
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Luming Zhang, Tetsuya Nomoto, Satoshi Yamashita, Hiroki Akutsu, Alexander I. Krivchikov, and Yasuhiro Nakazawa
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Physics and Astronomy (miscellaneous) ,General Physics and Astronomy - Abstract
The construction of a thermal conductivity measurement system designed for tiny molecules-based compounds is reported. We introduce complementary usage of chip-type RuO2 thermometers and E-type thermocouples in the sample part by using thin (ϕ 13μm) constantan and chromel wires. Two pairs of the constantan and chromel wires are used as lead wires for the four-terminal measurement of the resistance of RuO2 thermometers in the low-temperature region below about 20 K. Also, in the higher temperature region above 10 K up to room temperature with the overlapping range of 10-20 K, they are used as thermocouples for detecting temperature differences from that of the heat sink. We also compare a kind of resolution parameter of several sensors as a function of temperature to discuss the rational reason to select suitable sensors depending on the temperature region. Using the constructed apparatus, we report temperature dependences of the thermal conductivity of deuterated κ-(d8:BEDT-TTF)2Cu[N(CN)2]Br in a wide temperature range between 2 and 250 K. The result provides convincing evidence for the validity of the newly developed system for the thermal measurements of molecular crystals.
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- 2023
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6. Asymmetric N-heteroacene tetracene analogues as potential n-type semiconductors
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Andrew J. P. White, Mark Oxborrow, Max Attwood, Anthony Maho, Wern Ng, Sandrine Heutz, Joseph H. L. Hadden, Hao Wu, Hiroki Akutsu, Dong Kuk Kim, Engineering & Physical Science Research Council (EPSRC), and Engineering & Physical Science Research Council (E
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Technology ,Materials science ,Materials Science ,Heteroatom ,Materials Science, Multidisciplinary ,Crystal structure ,Physics, Applied ,ACENES ,chemistry.chemical_compound ,Materials Chemistry ,Molecule ,Thin film ,0912 Materials Engineering ,HOMO/LUMO ,0306 Physical Chemistry (incl. Structural) ,PENTACENE ,Science & Technology ,CRYSTAL ,DERIVATIVES ,Physics ,SUBSTITUTION ,0303 Macromolecular and Materials Chemistry ,General Chemistry ,STATE ,Organic semiconductor ,Crystallography ,Tetracene ,chemistry ,Physical Sciences ,THIN-FILM TRANSISTORS ,Single crystal - Abstract
In the search for high performance n-type organic semiconductors (OSCs) a simple strategy might be substitution of aromatic CH groups for nitrogen heteroatoms. Here, we report the synthesis and characterisation of two novel N-heteroacene compounds, namely, 1,5,12-triazatetracene (TrAT1) and 2,5,12-triazatetracene (TrAT2). Their potential as n-type materials is evaluated against 5,12-diazatetracene (DAT) by UV/vis and EPR spectroscopy, cyclic voltammetry, DFT, single crystal X-ray diffraction and thin film characterisation. Increasing the number of N-heteroatoms was found to stabilise the HOMO and LUMO leading to electron affinities for TrAT1 and TrAT2 of ca. −4 eV. Both compounds were found to exhibit columns of co-facial π-stacked molecules. For TrAT1, molecules are also linked by hydrogen bonding, while the crystal structure of TrAT2 was found to be inherently disordered. Thin films of DAT, TrAT1 and TrAT2 were grown by organic molecular beam deposition (OMBD) and found to form discontinuous films, where TrAT1 exhibited a preferential orientation.
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- 2021
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7. Structural, magnetic and Mössbauer spectroscopic studies of the [Fe(3-bpp)2](CF3COO)2 complex: role of crystal packing leading to an incomplete Fe(<scp>ii</scp>) high spin ⇋ low spin transition
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Djulia Onggo, Varimalla Raghavendra Reddy, Hiroki Akutsu, Ashis Bhattacharjee, Yasuhiro Nakazawa, Hari Sutrisno, and Kristian Handoyo Sugiyarto
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Diffraction ,Materials science ,Transition temperature ,Spin transition ,General Chemistry ,Condensed Matter Physics ,Crystal ,chemistry.chemical_compound ,Crystallography ,chemistry ,Mössbauer spectroscopy ,Pyridine ,General Materials Science ,Single crystal ,Spin-½ - Abstract
Single crystal X-ray diffraction, magnetic and 57Fe Mossbauer spectroscopic studies of a new iron(II)-based spin transition complex – [Fe(3-bpp)2](CF3COO)2 (bpp = 2,6-bis(pyrazol-3-yl)pyridine) are reported. The complex exhibits an incomplete thermal high spin (HS) low spin (LS) transition at ∼226 K which is not associated with any crystallographic transition. Only one of the two crystallographic iron(II) sites undergoes the spin transition, while the other HS site remains invariant of temperature down to 10 K. The origin of the incomplete spin transition is understood by analysing the nature of crystal packing below and above the transition temperature with special attention to the degree of distortion. The present study shows the role of the degree of distortion associated with the cations in the [Fe(3-bpp)2]2+ spin transition complexes.
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- 2021
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8. Chiral metal down to 4.2 K - a BDH-TTP radical-cation salt with spiroboronate anion B(2-chloromandelate)2−
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Hiroshi Nishimoto, Yasuhiro Nakazawa, Michael Brannan, Tomofumi Kadoya, Lee Martin, Hiroki Akutsu, Toby J. Blundell, and Jun-ichi Yamada
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chemistry.chemical_classification ,Chiral ligand ,Metals and Alloys ,Salt (chemistry) ,General Chemistry ,Crystal structure ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Metal ,Crystallography ,chemistry ,Radical ion ,visual_art ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Racemic mixture ,Enantiomer ,Chirality (chemistry) - Abstract
We report the first example of a chiral BDH-TTP radical-cation salt. Chirality is induced in the structure via the use of a chiral spiroboronate anion where three stereocentres are present, one on each chiral ligand and one on the boron centre. Despite starting from a labile racemic mixture of BS and BR enantiomers, only one enantiomer is present in the crystal lattice. The anions pack in a novel double anion layer which is the thickest anion layer found in a BDH-TTP salt. This material is chiral and shows metallic behaviour down to at least 4.2 K.
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- 2021
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9. Systematic study on thermal conductivity of organic triangular lattice systems β′-X[Pd(dmit)2]2
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Tetsuya Nomoto, Satoshi Yamashita, Hiroki Akutsu, Yasuhiro Nakazawa, and Reizo Kato
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- 2022
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10. Structure and Properties of a New Purely Organic Magnetic Conductor, δ′-(BEDT-TTF)2(PO-CONHCH(cyclopropyl)SO3)·1.7H2O
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Akiko Kohno, Scott S. Turner, Yasuhiro Nakazawa, and Hiroki Akutsu
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chemistry.chemical_classification ,chemistry.chemical_compound ,Crystallography ,chemistry ,010405 organic chemistry ,Salt (chemistry) ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Tetrathiafulvalene ,0104 chemical sciences ,Ion ,Conductor - Abstract
A new bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF)-based salt with an organic magnetic anion, PO-CONHCH(cyclopropyl)SO3−, has been prepared (PO = 2,2,5,5-tetramethyl-3-pyrrolin-1-oxyl free radi...
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- 2020
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11. Different electronic states of isomorphous chiral vs. racemic organic conducting salts, β′′-(BEDT-TTF)2(S- and rac-PROXYL-CONHCH2SO3)
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Satoshi Yamashita, Akiko Kohno, Scott S. Turner, Hiroki Akutsu, and Yasuhiro Nakazawa
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Materials science ,Point reflection ,02 engineering and technology ,Orders of magnitude (numbers) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Electronic states ,Metal ,Crystallography ,Chemistry (miscellaneous) ,Electrical resistivity and conductivity ,visual_art ,Atom ,visual_art.visual_art_medium ,General Materials Science ,0210 nano-technology ,Electronic band structure - Abstract
The chiral and racemic salts β′′-(BEDT-TTF)2(S- and rac-PROXYL-CONHCH2SO3) (S-2 and rac-2) are almost isomorphous apart from a deviation in the C–H bond direction at the chiral centre. Both salts are metallic at room temperature, with similar broad metal-insulator transitions. Band structure calculations of the chiral and racemic salts indicate that both electronic structures are quite similar. However, at 30 K, S-2 has a resistivity that is nearly three orders of magnitude higher than that of rac-2. The results suggest a significant effect of the broken inversion symmetry, due to the positional change of only one atom.
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- 2020
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12. Chiral molecular conductor with an insulator–metal transition close to room temperature
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Hiroki Akutsu, Jonathan I Short, Songjie Yang, Toby J. Blundell, Yasuhiro Nakazawa, Lee Martin, John D. Wallis, and Sara J. Krivickas
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Materials science ,Condensed matter physics ,Metals and Alloys ,Insulator (electricity) ,General Chemistry ,Conductivity ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Conductor ,Metal ,visual_art ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Chirality (chemistry) - Abstract
Materials exhibiting both chirality and conductivity do not exist in nature and very few examples have been synthesised. We report here the synthesis of a chiral molecular metal which remains metallic down to at least 4.2 K. This material also exhibits room-temperature switching capabilities with a transition upon cooling below 10 °C.
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- 2020
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13. Enhancements of Superconductivity and Insulating Electrical Resistivity under the Same Uniaxial Strain in a Molecular Conductor
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Yuichi Okii, Takashi Yamamoto, Toshio Naito, Kensuke Konishi, Hiroki Akutsu, and Yasuhiro Nakazawa
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General Physics and Astronomy - Published
- 2022
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14. Enantiopure and racemic radical-cation salts of B(mandelate)
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Toby J, Blundell, Jordan R, Lopez, Kathryn, Sneade, John D, Wallis, Hiroki, Akutsu, Yasuhiro, Nakazawa, Simon J, Coles, Claire, Wilson, and Lee, Martin
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We report the first examples of radical-cation salts of BEDT-TTF with spiroborate anions [B(mandelate)
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- 2022
15. Correlation-driven organic 3D topological insulator with relativistic fermions
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Tetsuya Nomoto, Shusaku Imajo, Hiroki Akutsu, Yasuhiro Nakazawa, and Yoshimitsu Kohama
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Condensed Matter - Strongly Correlated Electrons ,Multidisciplinary ,Strongly Correlated Electrons (cond-mat.str-el) ,General Physics and Astronomy ,FOS: Physical sciences ,General Chemistry ,General Biochemistry, Genetics and Molecular Biology - Abstract
Exploring new topological phenomena and functionalities induced by strong electron correlation has been a central issue in modern condensed-matter physics. One example is a topological insulator (TI) state and its functionality driven by the Coulomb repulsion rather than a spin-orbit coupling. Here, we report a "correlation-driven" TI state realized in an organic zero-gap system $\alpha$-(BETS)$_2$I$_3$. The surface metallic state that emerges at low temperatures exhibits characteristic transport properties of a gapless Dirac semimetal, evidencing the presence of a topological surface state in this compound. Moreover, we observe a topological phase switching between the TI state and non-equilibrium Dirac semimetal state by a dc current, which is a unique functionality of a correlation-driven TI state. Our findings demonstrate that correlation-driven TIs are promising candidates not only for practical electronic devices but also as a field for discovering new topological phenomena and phases., Comment: 36 pages including 10 figures
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- 2022
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16. Exceptionally high temperature spin crossover in amide-functionalised 2,6-bis(pyrazol-1-yl)pyridine iron(ii) complex revealed by variable temperature Raman spectroscopy and single crystal X-ray diffraction
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Pierre Le Maguere, Max Attwood, Lee Martin, Scott S. Turner, Hiroki Akutsu, and Toby J. Blundell
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Inorganic Chemistry ,symbols.namesake ,Crystallography ,Materials science ,Differential scanning calorimetry ,Spin states ,Hydrogen bond ,Spin crossover ,X-ray crystallography ,symbols ,Crystal structure ,Raman spectroscopy ,Single crystal - Abstract
The synthesis of a novel amide-functionalised 2,6-bis(pyrazol-1-yl)pyridine-4-carboxamide ligand (bppCONH2) is described. The complex salts [Fe(bppCONH2)2](BF4)2 and [Fe(bppCONH2)2](ClO4)2 were synthesised and characterised by SQUID magnetometry, differential scanning calorimetry, variable temperature Raman spectroscopy and single crystal X-ray diffraction. DSC measurements of [Fe(bppCONH2)2](BF4)2 indicate a spin-crossover (SCO) transition with T↑ at 481 K and T↓ at 461 K, showing a 20 K hysteresis. DSC for the perchlorate salt shows an SCO transition with T↑ at 459 K and T↓ at 445 K with a 14 K hysteresis. For the BF4− salt analysis of low and high-spin state crystal structures at 101, 290 and 500 K, suggest stabilisation of the low spin state due to the formation of 1D hydrogen-bonded cationic chains. Variable temperature Raman studies of the BF4 salt support the presence of a high temperature SCO. It is speculated that the presence of hysteresis may be attributed to differences in the inter-molecular hydrogen bonding in the low spin and high spin states.
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- 2021
17. Chiral metal down to 4.2 K - a BDH-TTP radical-cation salt with spiroboronate anion B(2-chloromandelate)
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Toby J, Blundell, Michael, Brannan, Hiroshi, Nishimoto, Tomofumi, Kadoya, Jun-Ichi, Yamada, Hiroki, Akutsu, Yasuhiro, Nakazawa, and Lee, Martin
- Abstract
We report the first example of a chiral BDH-TTP radical-cation salt. Chirality is induced in the structure via the use of a chiral spiroboronate anion where three stereocentres are present, one on each chiral ligand and one on the boron centre. Despite starting from a labile racemic mixture of BS and BR enantiomers, only one enantiomer is present in the crystal lattice. The anions pack in a novel double anion layer which is the thickest anion layer found in a BDH-TTP salt. This material is chiral and shows metallic behaviour down to at least 4.2 K.
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- 2021
18. Large-Amplitude Thermal Vibration-Coupled Valence Tautomeric Transition Observed in a Conductive One-Dimensional Rhodium-Dioxolene Complex
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Minoru Mitsumi, Hiroki Akutsu, Koshiro Toriumi, Haruo Akashi, Yasutaka Kitagawa, Masahiro Hashimoto, Yuji Miyazaki, and Yuuki Komatsu
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Phase transition ,Valence (chemistry) ,Chemistry ,Organic Chemistry ,chemistry.chemical_element ,General Chemistry ,Tautomer ,Catalysis ,Rhodium ,Vibration ,Amplitude ,X-ray photoelectron spectroscopy ,Chemical physics ,Thermal ,Physics::Atomic and Molecular Clusters - Abstract
The exploration of dynamic molecular crystals is a fascinating theme for materials scientists owing to their fundamental science and potential application to molecular devices. Herein, a one-dimensional (1D) rhodium-dioxolene complex is reported that exhibits drastic changes in properties with the phase transition. X-ray photoelectron spectroscopy (XPS) revealed that the room-temperature (RT) phase is in a mixed-valence state, and therefore, the drastic changes originate from the mixed-valence state appearing in the RT phase. Another notable feature is that the mean square displacements of the rhodium atoms along the 1D chain dramatically increased in the RT phase, indicating a large-amplitude vibration of the Rh-Rh bonds. From these results, a possible mechanism for the appearance of the mixed-valence state in the RT phase was proposed based on the thermal electron transfer from the 1D d-band to the semiquinonato π* orbital coupled with the large-amplitude vibration of the Rh-Rh bonds.
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- 2020
19. Anisotropic Fully-Gapped Superconductivity Possibly Mediated by Charge Fluctuations in a Nondimeric Organic Complex
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Masashi Tokunaga, Hiroki Akutsu, K. Kindo, Takeshi Yajima, Shusaku Imajo, Yoshimitsu Kohama, Yasuhiro Nakazawa, and Ryosuke Kurihara
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Superconductivity ,Physics ,Condensed matter physics ,Strongly Correlated Electrons (cond-mat.str-el) ,Condensed Matter - Superconductivity ,General Physics and Astronomy ,Quantum oscillations ,FOS: Physical sciences ,Charge (physics) ,Fermi surface ,01 natural sciences ,Heat capacity ,Superconductivity (cond-mat.supr-con) ,Condensed Matter - Strongly Correlated Electrons ,Pairing ,Condensed Matter::Superconductivity ,0103 physical sciences ,Organic superconductor ,010306 general physics ,Anisotropy - Abstract
We investigate low-temperature electronic properties of the nondimeric organic superconductor $\beta^{\prime\prime}$-(BEDT-TTF)$_4$[(H$_3$O)Ga(C$_2$O$_4$)$_3$]PhNO$_2$. By examining ultrasonic properties, charge disproportionation (CD) without magnetic field dependence is detected below $T_{\rm CD}$$\sim$8~K just above the superconducting critical temperature $T_{\rm c}$$\sim$6~K. From quantum oscillations in high fields, we find variation in the Fermi surface and mass enhancement induced by the CD. Heat capacity studies elucidate that the superconducting gap function is fully gapped in the Fermi surface, but anisotropic with fourfold symmetry. We point out that the pairing mechanism of the superconductivity is possibly dominated by charge fluctuations., Comment: 6 figures
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- 2020
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20. Construction of a thermal conductivity measurement system for small single crystals of organic conductors
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Satoshi Yamashita, Yasuhiro Nakazawa, Tetsuya Nomoto, Hiroki Akutsu, Alexander I. Krivchikov, and Shusaku Imajo
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Phase transition ,Materials science ,Drop (liquid) ,Analytical chemistry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,010406 physical chemistry ,0104 chemical sciences ,Thermal conductivity measurement ,chemistry.chemical_compound ,Thermal conductivity ,chemistry ,Molecule ,Physical and Theoretical Chemistry ,0210 nano-technology ,Electrical conductor ,Tetrathiafulvalene - Abstract
We newly constructed a thermal conductivity measurement system for single crystals of molecular compounds. This system enables us to measure the thermal conductivity of samples with the length of less than 1.0 mm. In order to evaluate the capability of detection of phase transitions occurred in molecule-based materials, we performed the thermal conductivity measurement of single crystals of organic conductors α-(BEDT-TTF)2I3 and κ-(BEDT-TTF)2Cu[N(CN)2]Br, where BEDT-TTF denotes bis(ethylenedithio)tetrathiafulvalene. From the temperature dependence of the thermal conductivity of α-(BEDT-TTF)2I3, we succeeded in observing the metal–insulator transition as a sudden drop of κ(T) at 135 K. In the temperature dependence of thermal conductivity of κ-(BEDT-TTF)2Cu[N(CN)2]Br, we could observe the increment of κ(T) at the metal-superconducting transition (Tc = 11.4 K). These results show that the newly developed system has high performance enough to detect various kinds of phase transitions in small crystals of molecular compounds.
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- 2018
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21. A new Ni(dmit)2-based organic magnetic charge-transfer salt, (m-PO-CONH-N-methylpyridinium)[Ni(dmit)2]·CH3CN
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Soichi Ito, Tomofumi Kadoya, Shin'ichi Nakatsuji, Jun-ichi Yamada, Hiroki Akutsu, Scott S. Turner, and Yasuhiro Nakazawa
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chemistry.chemical_classification ,Spins ,010405 organic chemistry ,Radical ,Salt (chemistry) ,Crystal structure ,010402 general chemistry ,01 natural sciences ,Magnetic susceptibility ,0104 chemical sciences ,Inorganic Chemistry ,Crystallography ,chemistry ,Ferromagnetism ,Mean field theory ,Materials Chemistry ,Physical and Theoretical Chemistry ,Spin (physics) - Abstract
A new Ni(dmit)2-based organic magnetic charge-transfer (CT) salt, (m-PO-CONH-N-methylpyridinium)[Ni(dmit)2]·CH3CN, where PO = 2,2,5,5-Tetramethyl-3-pyrrolin-1-oxyl free radical and dmit = 2-Thioxo-1,3-dithiole-4,5-dithiolate, was obtained, the crystal structure and magnetic properties of which are reported. Magnetic susceptibility of the CT salt obeys a combination of 1D ferromagnetic (1DF) Heisenberg (J1DF = +0.26 K) and Singlet-Triplet (ST) models (JST = -51.2 K) with mean field (MF) approximation (JMF = -6.7 K), suggesting that spins on the PO radicals form 1D ferromagnetic chains and spins on the Ni(dmit)2 monoanions forms spin dimers at low temperature, the latter of which was also confirmed by band calculations.
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- 2018
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22. Bulk Kosterlitz–Thouless Type Molecular Superconductor β″-(BEDT-TTF)2[(H2O)(NH4)2Cr(C2O4)3]·18-crown-6
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Jordan R. Lopez, Lee Martin, Shusaku Imajo, Hiroki Akutsu, and Yasuhiro Nakazawa
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Superconductivity ,Superstructure ,18-Crown-6 ,02 engineering and technology ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Magnetic field ,Ion ,Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,chemistry ,Molecule ,Physical and Theoretical Chemistry ,0210 nano-technology ,Critical field - Abstract
A new molecular superconductor, β”-(BEDTTTF)2[(H2O)(NH4)2Cr(C2O4)3].18-crown-6, has been synthesized from the organic donor molecule BEDT-TTF with the anion Cr(C2O4)3 3- . The crystal structure consists of conducting organic layers of BEDT-TTF molecules which adopt the β” packing motif (layer A), layers of NH4 + and Λ-Cr(C2O4)3 3- (layer B), layers of (H2O)(NH4)18- crown-6 (layer C), and layers of NH4 + and Δ-Cr(C2O4)3 3- (layer D) which produce a superstructure with a repeating pattern of ABCDABCDA. As a result of this packing arrangement this is the 2D superconductor with the widest gap between conducting layers where only a single donor packing motif is present (β”). Superconducting critical temperatures at ambient pressure observed by electrical transport and magnetic measurements are 4.0- 4.9 and 2.5 K, respectively. The strong 2D nature of this system, the broad transition to Tzero at 1.8K, and the transition of α of V ∝ Iα from 1 to 3 on I-V curves strongly suggests that the superconducting transition is very close to a Kosterlitz-Thouless transition. The magnetic field dependence of the superconducting critical temperature parallel to the conducting plane gives an upper critical field μ0Hc2// > 8 T, which is over the calculated Pauli-Clogston limit for this material.
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- 2017
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23. Anion polarity-induced self-doping in a purely organic paramagnetic conductor, α′-α′-(BEDT-TTF) 2 (PO-CONH- m -C 6 H 4 SO 3 )·H 2 O where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene and PO is the radical 2,2,5,5-Tetramethyl-3-pyrrolin-1-oxyl
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Shin'ichi Nakatsuji, Soich Ito, Scott S. Turner, Yasuhiro Nakazawa, Keita Ishihara, Jun-ichi Yamada, Hiroki Akutsu, and Fumiyoshi Nishiyama
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Stereochemistry ,Doping ,Fermi level ,02 engineering and technology ,Crystal structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Magnetic susceptibility ,0104 chemical sciences ,Ion ,Inorganic Chemistry ,Dipole ,Paramagnetism ,chemistry.chemical_compound ,Crystallography ,symbols.namesake ,chemistry ,Materials Chemistry ,symbols ,Physical and Theoretical Chemistry ,0210 nano-technology ,Tetrathiafulvalene - Abstract
A new BEDT-TTF-based salt with an organic free radical, α′-α′-(BEDT-TTF)2(PO-CONH-m-C6H4SO3)·H2O, has been prepared. The crystal structure consists of alternating donor and anion/water layers propagated along the c axis. The anisotropic radical anions form a head-to-head arrangement, which provides a permanent dipole moment. The effect on the nearest donor layer has been estimated to be 4.0 V. The salt has two crystallographically independent donor layers (A and B), one of which (A) is surrounded by the negative ends of the anion layer dipole whereas the B layers are bordered by the positive ends of the dipole. This structural feature suggests that layers A and B have different Fermi levels. To eliminate the imbalance, self-doping occurs whereby electron density is transferred from layer A to B. The temperature dependence of the magnetic susceptibility has 11.1% of extra Curie spins, from which a doping ratio of 12.7% has been estimated.
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- 2017
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24. Increase in the Magnetic Ordering Temperature (Tc) as a Function of the Applied Pressure for A2Mn[Mn(CN)6] (A = K, Rb, Cs) Prussian Blue Analogues
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M. Sugimoto, Christopher M. Kareis, Jack G. DaSilva, Shinsuke Yamashita, Hiroki Akutsu, Joel S. Miller, and Yasuhiro Nakazawa
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Prussian blue ,Chemistry ,Transition temperature ,Hydrostatic pressure ,Analytical chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,Magnetization ,chemistry.chemical_compound ,Nuclear magnetic resonance ,Ferrimagnetism ,Physical and Theoretical Chemistry ,0210 nano-technology ,Néel temperature ,Ambient pressure ,Monoclinic crystal system - Abstract
Magnetization measurements under pressure reveal that the external hydrostatic pressure significantly increases in the ferrimagnetic transition temperature, Tc, for A2Mn[Mn(CN)6] (A = K, Rb, Cs). In the case of monoclinic A = K and Rb, dTc/dp values are 21.2 and 14.6 K GPa–1, respectively, and Tc increases by 53 and 39%, respectively, from ambient pressure to 1.0 GPa. The cubic A = Cs compound also shows a monotonous increase with an initial rate of 4.22 K GPa–1 and about 11.4 K GPa–1 above 0.6 GPa, and an overall Tc increase by 26% at 1.0 GPa. The increase in Tc is attributed to deformation of the structure such that the MnII—N≡C angle decreases with increasing pressure. The smaller the alkali cation, the greater the decrease in the MnII—N≡C angle induced by pressure and the larger the increase of dTc/dp. This is in accordance with the ambient-pressure structures for A2Mn[Mn(CN)6] (A = K, Rb, Cs), which have decreasing MnII—N≡C angles that correlate to the observed increasing Tcs as K > Rb > Cs. The larg...
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- 2017
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25. Enantiopure and racemic radical-cation salts of bis(2′-hydroxylpropylthio)(ethylenedithio)TTF with polyiodide anions
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Anthony Christian, Shin'ichi Nakatsuji, Milena A. Guziak, Hiroki Akutsu, Peter Maksymiw, Lee Martin, John D. Wallis, Jun-ichi Yamada, and Florence Konalian-Kempf
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Stereochemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,Polyiodide ,Crystallography ,Enantiopure drug ,chemistry ,Radical ion ,Side chain ,Molecule ,Triiodide ,Enantiomer ,0210 nano-technology ,Tetrathiafulvalene - Abstract
The chiral TTF-based donor molecule bis(2′-hydroxylpropylthio)(ethylenedithio)tetrathiafulvalene (BHPT-EDT-TTF) has produced enantiopure R,R and S,S radical-cation salts with polyiodide anions I3− and I82−. Enantiomorphic 6 : 6 donor : I3 phases grown from either the R,R or S,S donor are semiconducting with similar activation energies of 0.24–0.30 eV and 0.22–0.23 eV, respectively, and contain three unique face-to-face donor pairs whose relative orientation is determined by side chain conformations and hydrogen bonding. Racemic material under the same conditions gave an insulating centrosymmetric phase with R,R and S,S donor cations in a face-to-face pair partnered with an octaiodide dianion, and with a ca. 3 : 1 disorder between the enantiomers. Enantiopure BHPT-EDT-TTF yielded two further insulating crystalline phases of composition 2 : 2 with triiodide and 2 : 1 with octaiodide.
- Published
- 2017
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26. Multilayer Coated Microstructure for Solar Selective Absorbers
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Hiroo Yugami, Hiroki Akutsu, Masafumi Kumano, Makoto Shimizu, Shinichiro Tsuda, and Kosuke Hikichi
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010302 applied physics ,Materials science ,Mechanical Engineering ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Atomic layer deposition ,Thermal radiation ,0103 physical sciences ,Electrical and Electronic Engineering ,Composite material ,0210 nano-technology ,Periodic microstructure - Published
- 2017
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27. Effects of electron correlations and chemical pressures on superconductivity of β′′ -type organic compounds
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Alexander L. Morritt, A Akutsu-Sato, Yasuhiro Nakazawa, Hiroki Akutsu, Shusaku Imajo, and Lee Martin
- Subjects
Superconductivity ,chemistry.chemical_compound ,Materials science ,Effective mass (solid-state physics) ,Electrical resistance and conductance ,chemistry ,Chemical physics ,Pairing ,Condensed Matter::Strongly Correlated Electrons ,Disproportionation ,Electron ,Tetrathiafulvalene ,Magnetic field - Abstract
We investigate low-temperature electronic states of the series of organic conductors β'' - [bis(ethylenedithio)tetrathiafulvalene] 4[(H3O)M(C2O4)3] G, where M and G represent trivalent metalions and guest organic molecules, respectively. Our structural analyses reveal that the replacement of M and G give rise to systematic change in the cell parameters, especially in the b-axis length, which has a positive correlation with the superconducting transition temperature Tc. Analysis of temperature and magnetic field dependences of the electrical resistance including the Shubnikov–de Haas oscillations elucidates that the variation of charge disproportionation, the effective mass, and the number of itinerant carriers can be systematically explained by the change of the b-axis length. The changes of the transfer integrals induced by stretching/compressing the b axis are confirmed by the band calculation. We discuss that electron correlations in quarter-filled electronic bands lead to charge disproportionation and the possibility of a novel pairing mechanism of superconductivity mediated by charge degrees of freedom.
- Published
- 2019
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28. 2D Molecular Superconductor to Insulator Transition in the β'-(BEDT-TTF)
- Author
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Alexander L, Morritt, Jordan R, Lopez, Toby J, Blundell, Enric, Canadell, Hiroki, Akutsu, Yasuhiro, Nakazawa, Shusaku, Imajo, and Lee, Martin
- Abstract
The series of salts β''-(BEDT-TTF)
- Published
- 2019
29. 2D Molecular Superconductor to Insulator Transition in the β′′- (BEDT-TTF)2[(H2O)(NH4)2M(C2O4)3]·18-crown‑6 Series (M = Rh, Cr, Ru, Ir)
- Author
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Enric Canadell, Toby J. Blundell, Hiroki Akutsu, Jordan R. Lopez, Lee Martin, Alexander L. Morritt, Yasuhiro Nakazawa, Shusaku Imajo, Japan Society for the Promotion of Science, Royal Society (UK), Ministerio de Ciencia, Innovación y Universidades (España), and Generalitat de Catalunya
- Subjects
Inorganic Chemistry ,Superconductivity ,chemistry.chemical_compound ,Crystallography ,chemistry ,Series (mathematics) ,010405 organic chemistry ,18-Crown-6 ,Physical and Theoretical Chemistry ,Insulator (genetics) ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences - Abstract
The series of salts β′′-(BEDT-TTF)2[(H2O)(NH4)2M(C2O4)3]·18-crown-6 show ambient-pressure superconductivity when M = Cr, Rh. Evidence indicates that the previously reported Cr and Rh salts show a bulk Berezinski–Kosterlitz–Thouless superconducting transition. The isostructural ruthenium and iridium salts are reported here. The Ir salt represents the first radical-cation salt to contain a 5d tris(oxalato)metalate anion. The Ru and Ir salts do not show superconductivity but instead undergo a broad chemically induced metal to insulator transition at 155 K for ruthenium and at 100 K for iridium. The c axes of the Ru and Ir salts are much shorter than those of the Rh and Cr salts. Thus, the more stable metallic state of the Cr and Rh salts is associated with the more strongly 2D electronic systems. The different low-temperature behavior of the Ru and Ir salts, which exhibit a smaller interlayer spacing, could originate from a structural change in the anionic layer which thus can be easily transmitted to the donor layers and generate a localized state. However, another possibility is that it originates from Berezinski–Kosterlitz–Thouless effects., This work has been supported by a Royal Society Leverhulme Trust Senior Research Fellowship, and the JSPS (KAKENHI Grant Number JP17H01144) and Royal Society (Research Grants (RG100853 and RG081209), International Exchange Scheme (IE130367 and IE150152), and International Joint Project (JP0869972)). L.M. thanks the Royal Society and Leverhulme Trust for a Senior Research Fellowship. J.R.L. and L.M. thank Nottingham Trent University for Ph.D. funding. E.C. acknowledges support by the MICIU (Spain) through Grant PGC2018-096955-BC44 and the Severo Ochoa Centers of Excellence Program (Grant SEV-2015-0496) as well as by the Generalitat de Catalunya (2017SGR1506).
- Published
- 2019
30. Lattice and Charge Fluctuations in a Molecular Superconductor
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Hiroki Akutsu, Toshio Naito, Mikio Uruichi, Yasuhiro Nakazawa, and Takashi Yamamoto
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Superconductivity ,Lattice (module) ,symbols.namesake ,Materials science ,Condensed matter physics ,Condensed Matter::Superconductivity ,symbols ,General Physics and Astronomy ,Superconducting transition temperature ,Condensed Matter::Strongly Correlated Electrons ,Charge (physics) ,Raman spectroscopy ,Astrophysics::Galaxy Astrophysics - Abstract
We report IR and Raman spectra for a two-dimensional superconductor, β′′-(BEDT-TTF)4[Ga(C2O4)3(H3O)]C6H5NO2, below the superconducting transition temperature. The behavior of the lattice-sensitive ...
- Published
- 2021
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31. New Family of Six Stable Metals with a Nearly Isotropic Triangular Lattice of Organic Radical Cations and Diluted Paramagnetic System of Anions: κ(κ⊥)-(BDH-TTP)4MX4·Solv, where M = CoII, MnII; X = Cl, Br, and Solv = (H2O)5, (CH2X2)
- Author
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A. A. Bardin, Jun-ichi Yamada, and Hiroki Akutsu
- Subjects
Chemistry ,Isotropy ,Inorganic chemistry ,02 engineering and technology ,General Chemistry ,Electronic structure ,Crystal structure ,Conductivity ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Ion ,Paramagnetism ,Crystallography ,General Materials Science ,Hexagonal lattice ,Isostructural ,0210 nano-technology - Abstract
A new family of six paramagnetic metals, namely, κ-(BDH-TTP)4CoCl4·(H2O)5 (I), κ-(BDH-TTP)4Co0.54Mn0.46Cl4·(H2O)5 (II), κ-(BDH-TTP)4MnCl4·(H2O)5 (III), κ⊥-(BDH-TTP)4CoBr4·(CH2Cl2) (IV), κ⊥-(BDH-TTP)4MnBr4·(CH2Cl2) (V), and κ⊥-(BDH-TTP)4MnBr4·(CH2Br2) (VI), has been synthesized and characterized by X-ray crystallography, four-probe conductivity measurements, SQUID magnetometry, and calculations of electronic structure. The newly discovered κ⊥-type packing motif of organic layers differs from the parent κ-type by a series of longitudinal shifts of BDH-TTP radical cations in the crystal structure. Salts I–VI form two isostructural groups: I–III (κ) and IV–VI (κ⊥). Salts I–III are isostructural to the previously discovered κ-(BDH-TTP)2FeIIIX4 (X = Cl, Br) even though the charge of FeX4– anions is half that of the MX42– (M = Co, Mn) anions. The tetrahedral anions are disordered in I–III but completely ordered in IV–VI. The type of included solvent molecule is solely determined by the anion size. The paramagnet...
- Published
- 2016
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32. Thermal anomaly around the superconductive transition of κ-(BEDT-TTF)2Cu(NCS)2 with external pressure and magnetic field control
- Author
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Shusaku Imajo, Yuki Muraoka, Satoshi Yamashita, Yasuhiro Nakazawa, and Hiroki Akutsu
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Superconductivity ,Condensed matter physics ,Chemistry ,Transition temperature ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Heat capacity ,Magnetic field ,Condensed Matter::Superconductivity ,Phase (matter) ,0103 physical sciences ,Condensed Matter::Strongly Correlated Electrons ,Physical and Theoretical Chemistry ,Anomaly (physics) ,010306 general physics ,0210 nano-technology ,Ambient pressure ,Phase diagram - Abstract
The temperature dependence of the ac heat capacity of a molecule-based superconductor κ-(BEDT-TTF)2Cu(NCS)2 under external pressures and with magnetic fields is reported. A peak structure in C p T −1 due to the superconductive transition was observed around 9 K at ambient pressure. This peak is suppressed by applying magnetic fields up to 7 T. The systematic decrease in the transition temperature with the increase in external pressure is confirmed by thermodynamic measurements under 0.15, 0.30 and 0.45 GPa. Through the analysis of the peak shape of the thermal anomaly, it is suggested that the gradual suppression of the coupling strength of the superconductivity occurs with the increase in pressure. This feature is consistent with the argument based on the chemical pressure effect in the superconductive phase of κ-(BEDT-TTF)2 X system, where X denotes mono-valence counter anions. The result demonstrates that the appearance of the Fermi-liquid character produced by applying pressure in the dimer-Mott phase diagram affects the nature and the coupling feature of the superconductivity. Importance of high-pressure heat capacity for molecule-based compounds is emphasized.
- Published
- 2016
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33. Variation of Electronic Heat Capacity of κ-(BEDT-TTF)2Cu[N(CN)2]Br Induced by Partial Substitution of Donor Layers
- Author
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Emre Yesil, Hiroki Akutsu, Tetsuya Nomoto, Yasuhiro Nakazawa, Shusaku Imajo, and Satoshi Yamashita
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Crystallography ,Materials science ,Organic superconductor ,General Physics and Astronomy ,Molecule ,Partial substitution ,Heat capacity - Abstract
Low temperature thermodynamic properties of an organic superconductor κ-[(BEDT-TTF)0.95(BEDSe-TTF)0.05]2Cu[N(CN)2]Br where 5% of donor molecules of κ-(BEDT-TTF)2Cu[N(CN)2]Br are substituted by BEDS...
- Published
- 2020
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34. Thermodynamic properties of glassy phonon states induced by strong electron correlations in 𝜃-type organic charge transfer salts
- Author
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Yasuhiro Nakazawa, Shinsuke Yamashita, Hiroki Akutsu, Tetsuya Nomoto, and E. Yesil
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chemistry.chemical_classification ,Materials science ,Phonon ,Salt (chemistry) ,Statistical and Nonlinear Physics ,Charge (physics) ,02 engineering and technology ,Electron ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,chemistry ,Chemical physics ,0103 physical sciences ,Condensed Matter::Strongly Correlated Electrons ,Boson peak ,010306 general physics ,0210 nano-technology - Abstract
The appearance of electron correlations–induced glassy state of low-energy phonons in the non-dimeric organic charge transfer salt in [Formula: see text]-(BEDT-TTF)2CsZn(SCN)4 is considered as a strong evidence of charge lattice coupling in molecular charge transfer salts. We discuss the temperature and the magnetic field dependences of the heat capacity of this salt in terms of the soft potential model to describe the thermodynamic properties of enhanced phonons that occur in molecular glasses. The evaluated [Formula: see text] term of [Formula: see text]-(BEDT-TTF)2CsZn(SCN)4 is about 30 mJ K[Formula: see text] mol[Formula: see text], which is much larger than other charge transfer salts described by the low-temperature approximation of the Debye model. The magnetic fields dependence of the boson peak is almost negligible, but the low-energy term, for example, in the temperature-linear term of heat capacity shows a slight change, probably due to the small amount of localized spin moments. The comparison with other systems is also performed.
- Published
- 2020
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35. Development of frequency tuning AC modulation method for high-pressure heat capacity measurements of molecules-based compounds
- Author
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T. Maruyama, Hiroki Akutsu, Yasuhiro Nakazawa, Tetsuya Nomoto, and Shinsuke Yamashita
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Materials science ,business.industry ,Measure (physics) ,Statistical and Nonlinear Physics ,02 engineering and technology ,Calorimetry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Heat capacity ,Modulation ,High pressure ,0103 physical sciences ,Optoelectronics ,Molecule ,Development (differential geometry) ,Cube ,010306 general physics ,0210 nano-technology ,business - Abstract
The automatic frequency tuning method in the high-pressure ac calorimetry system constructed to measure heat capacity for molecules-based compounds with CuBe[Formula: see text]+[Formula: see text]NiCrAl cramp-type pressure cell is reported. This development is performed for increasing resolution and temperature ranges of the heat capacity measurements under external pressure up to 2.0 GPa. The system can check the appropriate conditions by tracing frequency dependence of [Formula: see text] to determine the oscillation frequency at the center of the plateau region of this value. The experiments using the powder samples of metal complexes clarified that the appropriate frequency changes sensitively depending on the difference of temperature and that of external pressures, especially at low temperature region. It decreases with increasing temperature and this relation was found to be almost linear with temperature in ambient pressure and under pressure conditions. The change of thermal diffusion from the sample part to the heat bath should be treated carefully in order to get enough resolution in high pressure AC heat capacity measurements of molecule-based compounds.
- Published
- 2020
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36. Fulde-Ferrell-Larkin-Ovchinnikov superconductivity in the layered organic superconductor β'−(BEDT−TTF)4[(H3O)Ga(C2O4)3]C6H5NO2
- Author
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Kaori Sugii, Taichi Terashima, Naoki Kikugawa, D. Graf, S. Uji, Peter Day, Y. Iida, Syuma Yasuzuka, Yasuhiro Nakazawa, Takayuki Isono, Hiroki Akutsu, and Shiori Sugiura
- Subjects
Condensed Matter::Quantum Gases ,Superconductivity ,Physics ,Phase transition ,Magnetic moment ,Condensed matter physics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Condensed Matter::Superconductivity ,0103 physical sciences ,Organic superconductor ,Diamagnetism ,Josephson vortex ,010306 general physics ,0210 nano-technology ,Critical field ,Phase diagram - Abstract
Resistance and magnetic torque measurements are reported in a layered organic superconductor, $\ensuremath{\beta}''\ensuremath{-}{(\mathrm{BEDT}\ensuremath{-}\mathrm{TTF})}_{4}[({\mathrm{H}}_{3}\mathrm{O})\mathrm{Ga}{({\mathrm{C}}_{2}{\mathrm{O}}_{4})}_{3}]{\mathrm{C}}_{6}{\mathrm{H}}_{5}{\mathrm{NO}}_{2}$ with ${T}_{c}=4.8$ K, where BEDT-TTF stands for bis(ethylenedithio)tetrathiafulvalene. Because of the large anion between the BEDT-TTF conducting layers, the superconductivity of this salt is highly anisotropic. In magnetic fields parallel to the conducting layers for $T=0.4$ K, the magnetic torque shows a large diamagnetic signal associated with hysteresis up to $\ensuremath{\sim}21$ T, suggesting the upper critical field ${H}_{c2}\ensuremath{\gtrsim}21$ T at 0.4 K. The large reduction of the diamagnetic signal is observed above 16 T, which shows a Fulde and Ferrell and Larkin and Ovchinnikov (FFLO) phase transition. For $T=0.5$ K, the interlayer resistance has nonzero value in a wide field region up to ${H}_{c2}$, arising from the Josephson vortex dynamics. Successive dips in the second derivative curves of the resistance are observed between 16 T and ${H}_{c2}$, which are ascribed to the commensurability effect between the Josephson vortex lattice and the order parameter oscillation of the FFLO phase. The commensurability effect is observed only in nearly parallel fields, showing that the FFLO phase is stable in a very limited field angle region. The temperature-field phase diagram is determined.
- Published
- 2018
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37. Radical-cation salt with novel BEDT-TTF packing motif containing tris(oxalato)germanate(IV)
- Author
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Jordan R. Lopez, Hiroki Akutsu, and Lee Martin
- Subjects
Tris ,Materials science ,Mechanical Engineering ,Inorganic chemistry ,Metals and Alloys ,Crystal structure ,Activation energy ,Conductivity ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Ion ,Crystallography ,chemistry.chemical_compound ,Radical ion ,chemistry ,Mechanics of Materials ,Electrical resistivity and conductivity ,Materials Chemistry ,Germanate - Abstract
The synthesis, crystal structure and resistivity of a new semiconducting BEDT-TTF radical-cation salt containing the tris(oxalato)germanate(IV) anion is reported. BEDT-TTF 4 [Ge(C 2 O 4 ) 3 ].0.5dichloromethane crystallizes in the space group P 2 1 / c, a = 18.322(7), b = 11.919(4), c = 32.746(11) A, β = 105.797(5)°, V = 6881(4) A 3 , T = 295(1) K, Z = 4. Electrical resistivity measurements show that BEDT-TTF 4 [Ge(C 2 O 4 ) 3 ].0.5dichloromethane is a semiconductor with an activation energy of 0.224 eV and room temperature resistivity of 212 Ω cm.
- Published
- 2015
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38. Structures and properties of diradical compounds containing disulfide and nitroxide groups
- Author
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Hiroki Akutsu, Kouki Fujikura, Shin'ichi Nakatsuji, Masaharu Satoh, and Jun-ichi Yamada
- Subjects
Nitroxide mediated radical polymerization ,Chemistry ,Diradical ,Mechanical Engineering ,Inorganic chemistry ,Metals and Alloys ,Disulfide bond ,Charge density ,Crystal structure ,Condensed Matter Physics ,Nitroxide radical ,Redox ,Electronic, Optical and Magnetic Materials ,Crystallography ,Mechanics of Materials ,Materials Chemistry ,Cyclic voltammetry - Abstract
In order to develop a kind of dual redox system with rechargeable battery property having potential high charge density, eight disulfide compounds carrying nitroxide radical have been prepared. Reflecting their multi-redox nature observed in their cyclic voltammetry data, they exhibit multi-step charge–discharge profiles with fairly large capacities over 200 Ah kg−1 for the first discharging processes. The Curie–Weiss type behaviors or 1D Heisenberg type profiles found for the respective radical compounds could be understandable by investigating the clarified crystal structures of four compounds (3, 4, 7, and 8) among them.
- Published
- 2015
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39. Cooling-rate-controlled heat capacity measurements of organic superconductor (TMTSF)2ClO4
- Author
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Ryo Yoshimoto, Yasuhiro Nakazawa, Satoshi Morishita, Shuhei Fukuoka, Hiroki Akutsu, and Satoshi Yamashita
- Subjects
Condensed matter physics ,Chemistry ,Slow cooling ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Heat capacity ,Ion ,Crystal ,Cooling rate ,0103 physical sciences ,Thermal ,Organic superconductor ,Physical and Theoretical Chemistry ,Anomaly (physics) ,010306 general physics ,0210 nano-technology - Abstract
An experimental technique for controlling cooling rate at low-temperature region in the heat capacity measurements was developed, and results of the heat capacity measurements of organic superconductor (TMTSF)2ClO4 cooled down with various cooling rates are presented. We succeeded in obtaining heat capacity data for a single piece of a crystal down to 0.7 K to study electronic states attained with slow cooling rates to extremely high cooling rate up to 500 K min−1. In the case of slow cooling at 0.17 K min−1, we observed a distinct peak of the superconductive transition which is almost consistent with previous results. The fraction of superconductive part is reduced in faster cooling rates, and no distinct peak structure in C p T −1 versus T 2 plot is observed around T c in the data of higher rate than 1.3 K min−1. In the rapid cooling region of 200 K min−1, clear reduction in electron density of states reflected in the change of the normal state γ value in the electronic heat capacity was observed. The sample shows an insulating character with a charge gap in the case of rapid cooling of 500 K min−1. We also discuss the feature of thermal anomaly related to the anion ordering around 24 K. A kind of glass-like freezing in residual conformational dynamics is suggested from the step-like decrease in C p T −1 around 19 K.
- Published
- 2015
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40. Chiral Radical‐Cation Salts of BEDT‐TTF Containing a Single Enantiomer of Tris(oxalato)aluminate(III) and ‐chromate(III)
- Author
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Lee Martin, Michael B. Hursthouse, Peter N. Horton, Ross W. Harrington, Hiroki Akutsu, and William Clegg
- Subjects
Tris ,chemistry.chemical_classification ,Nitromethane ,Aluminate ,Inorganic chemistry ,Salt (chemistry) ,Oxalate ,Inorganic Chemistry ,chemistry.chemical_compound ,Metallate ,chemistry ,Polymer chemistry ,Enantiomer ,Chirality (chemistry) - Abstract
Radical-cation salts of BEDT-TTF with chiral anions provide the opportunity to combine chirality with conductivity in the same molecular material. We report here two salts, (BEDT-TTF)3NaAl(C2O4)3·nitromethane and (BEDT-TTF)3(NH4)0.83Cr1.17(C2O4)3·nitromethane. The former crystallises in space group P21 and the latter in P212121. The use of nitromethane alone as the electrolyte for electrocrystallisation produces no crystals, but the addition of chiral (R)-(–)-carvone yields crystals of these two new chiral radical-cation salts of BEDT-TTF through chiral induction from racemic tris(oxalato)aluminate(III) and tris(oxalato)chromate starting materials. The honeycomb anion layers in these salts contain a single enantiomer of tris(oxalato)metallate and creates hexagonal cavities that are smaller than those found in the superconducting β″ salts in this tris(oxalate)metallate family, which gives preference for smaller solvents to be included, such as nitromethane. The chromium salt has a non-stoichiometric composition of the anion layer, which provides an electron doping effect to the donor layer.
- Published
- 2015
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41. Chirality in charge-transfer salts of BEDT-TTF of tris(oxalato)chromate(III)
- Author
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Michael B. Hursthouse, Hiroki Akutsu, Peter N. Horton, and Lee Martin
- Subjects
Tris ,Chromate conversion coating ,Chemistry ,Inorganic chemistry ,Charge (physics) ,General Chemistry ,Electrolyte ,Condensed Matter Physics ,Tris(oxalato)chromate(III) ,law.invention ,Ion ,chemistry.chemical_compound ,law ,Polymer chemistry ,General Materials Science ,Crystallization ,Chirality (chemistry) - Abstract
Crystallisation from chiral electrolyte (R)-(−)-carvone has produced three new chiral semiconducting salts of BEDT-TTF from racemic anion tris(oxalato)chromate(III).
- Published
- 2015
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42. Bulk Kosterlitz-Thouless Type Molecular Superconductor β″-(BEDT-TTF)
- Author
-
Lee, Martin, Jordan R, Lopez, Hiroki, Akutsu, Yasuhiro, Nakazawa, and Shusaku, Imajo
- Abstract
A new molecular superconductor, β″-(BEDT-TTF)
- Published
- 2017
43. Ambient-pressure molecular superconductor with a superlattice containing layers of tris(oxalato)rhodate enantiomers and 18-crown-6
- Author
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Hiroki Akutsu, Alexander L. Morritt, Jordan R. Lopez, Yoshihiko Ihara, Lee Martin, Shusaku Imajo, and Yasuhiro Nakazawa
- Subjects
Tris ,Superconductivity ,Condensed matter physics ,Superlattice ,18-Crown-6 ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Magnetic susceptibility ,0104 chemical sciences ,Ion ,Inorganic Chemistry ,chemistry.chemical_compound ,Crystallography ,chemistry ,Physical and Theoretical Chemistry ,0210 nano-technology ,Hybrid material ,Ambient pressure - Abstract
We report a novel multilayered organic–inorganic hybrid material, β″-(BEDT-TTF)2[(H2O)(NH4)2Rh(C2O4)3]·18-crown-6. This is the first molecular superconductor to have a superlattice with layers of both BEDT-TTF and 18-crown-6 and also the first with the anion tris(oxalato)rhodate. This is the 2D superconductor with the widest gap between conducting layers, where only a single donor packing motif is observed (β″). The strong 2D nature of this system strongly suggests that the superconducting transition is a Kosterlitz–Thouless transition. A superconducting Tc of 2.7 K at ambient pressure was found by transport measurements and 2.5 K by magnetic susceptibility measurements.
- Published
- 2017
44. Stereoisomeric semiconducting radical cation salts of chiral bis(2-hydroxypropylthio)ethylenedithioTTF with tetrafluoroborate anions
- Author
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John D. Wallis, Hiroki Akutsu, Lee Martin, Shin'ichi Nakatsuji, Jordan R. Lopez, Jun-ichi Yamada, Milena A. Guziak, and Jack Oxspring
- Subjects
chemistry.chemical_classification ,Tetrafluoroborate ,Chemistry ,Stereochemistry ,Salt (chemistry) ,General Chemistry ,Crystal structure ,Condensed Matter Physics ,chemistry.chemical_compound ,Crystallography ,Enantiopure drug ,Radical ion ,General Materials Science ,Orthorhombic crystal system ,Isostructural ,Monoclinic crystal system - Abstract
The new chiral TTF-based donor molecule bis(2-hydroxypropylthio)ethylenedithiotetrathiafulvalene has produced enantiopure R,R and S,S radical cation salts with the tetrafluoroborate anion as well as the nearly isostructural meso/racemate mixture. The enantiopure R,R or S,S salts are both 1:1 semiconducting salts with activation energies of 0.19–0.24 eV, both crystallising in the orthorhombic space group C2221. The semiconducting salt containing both meso and racemic donor cations has a very similar crystal structure but crystallising in the monoclinic space group C2/c (β = 91.39°) with similar S⋯S interactions but a smaller activation energy of 0.15–0.17 eV. This is in contrast to previous families of this type where the disordered racemate has a larger activation energy than its enantiopure salts.
- Published
- 2014
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45. Phonon Glass Induced by Electron Correlation
- Author
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Tetsuya Nomoto, Satoshi Yamashita, Hiroki Akutsu, Alexander I. Krivchikov, and Yasuhiro Nakazawa
- Subjects
Materials science ,Electronic correlation ,Condensed matter physics ,Phonon ,General Physics and Astronomy ,01 natural sciences ,010305 fluids & plasmas ,Organic semiconductor ,chemistry.chemical_compound ,Thermal conductivity ,chemistry ,0103 physical sciences ,010306 general physics ,Tetrathiafulvalene - Abstract
We report the glass-like thermal conductivity behavior of two charge-glass (CG) formers in θ-type organic semiconductors composed by bis(ethylenedithio)tetrathiafulvalene (abbreviated as BEDT-TTF) ...
- Published
- 2019
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46. Electrolyte‐Gating‐Induced Metal‐Like Conduction in Nonstoichiometric Organic Crystalline Semiconductors under Simultaneous Bandwidth Control
- Author
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Hiroshi Ito, Yusuke Edagawa, Reiji Kumai, Masayuki Suda, Hiroki Akutsu, Taishi Takenobu, Yoshitaka Kawasugi, Hiroshi Yamamoto, Rie Haruki, and Jiang Pu
- Subjects
Bandwidth management ,Materials science ,business.industry ,Gating ,Electrolyte ,Condensed Matter Physics ,Thermal conduction ,Metal ,Semiconductor ,visual_art ,visual_art.visual_art_medium ,Optoelectronics ,General Materials Science ,business - Published
- 2019
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- View/download PDF
47. Gap Symmetry of the Organic Superconductor λ-(BETS)2GaCl4 Determined by Magnetic-Field-Angle-Resolved Heat Capacity
- Author
-
Shusaku Imajo, Hiroki Akutsu, Satoshi Yamashita, Takuya Kobayashi, Yasuhiro Nakazawa, Atsushi Kawamoto, and Hiroya Kumagai
- Subjects
Materials science ,Condensed matter physics ,0103 physical sciences ,Organic superconductor ,General Physics and Astronomy ,Polar coordinate system ,010306 general physics ,01 natural sciences ,Heat capacity ,Symmetry (physics) ,010305 fluids & plasmas ,Magnetic field - Abstract
Angle-resolved heat capacity (ARHC) measurements with multi-directional magnetic fields for an organic superconductor λ-(BETS)2GaCl4 are performed to investigate the out-of-plane (polar angle) and ...
- Published
- 2019
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48. A spin resonance investigation of magnetism and dynamics in the charge-transfer salts beta'-(BEDT-TTF)(4)[(H3O)M(C2O4)(3)]S
- Author
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Alessandro Narduzzo, Luca Pardi, Arzhang Ardavan, Peter Day, Amalia I. Coldea, Hiroki Akutsu, V. Bercu, A Akutsu-Sato, John Singleton, and Scott S. Turner
- Subjects
Superconductivity ,Materials science ,Condensed matter physics ,Magnetism ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Ion ,Metal ,Local symmetry ,visual_art ,visual_art.visual_art_medium ,Molecule ,Antiferromagnetism ,Diamagnetism ,General Materials Science ,Condensed Matter::Strongly Correlated Electrons - Abstract
We report a spin resonance study of the family of quasi-two-dimensional organic (super)conductors β′-(BEDT-TTF) 4 [(H 3O)M(C 2O 4) 3]S, where M is a 3d transition metal ion and S is a host solvent molecule. The spin systems for M = Cr 3+ (S = 3/2) and M = Fe 3+ (S = 5/ 2) are investigated by means of both resonant and field modulation techniques in the frequency range between 50 and 313 GHz. The role of the different solvent molecules in determining the degree of spin-orbit coupling and the local symmetry at the metal ion site is established. The low temperature behaviour of intensities, positions and widths of the resonant lines shows significant modifications of the spin-orbit coupling, and of the inter-and intra-ionic spin-spin inter actions. Despite the onset of a weak antiferromagnetic internal field at low temperature, the ultimate narrowing of the lines suggests spin-lattice interactions may still be the dominant relaxation process. Diamagnetic screening in the mixed state of the superconducting samples for fields parallel to the quasi-two-dimensional layers induces additional lineshifts only below B = 2.5T and T = 4K, determining the threshold of full field penetration within the anion layers. © Springer Science+Business Media, LLC.
- Published
- 2016
- Full Text
- View/download PDF
49. Enantiopure and racemic radical-cation salts of B(malate)2(-) anions with BEDT-TTF
- Author
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Jordan R. Lopez, Jun-ichi Yamada, Tomofumi Kadoya, John D. Wallis, Lee Martin, Simon J. Coles, Hiroki Akutsu, Claire Wilson, and Yasuhiro Nakazawa
- Subjects
chemistry.chemical_classification ,Denticity ,010405 organic chemistry ,Chemistry ,Stereochemistry ,Ligand ,Diastereomer ,chemistry.chemical_element ,Salt (chemistry) ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,Ion ,Inorganic Chemistry ,Enantiopure drug ,Radical ion ,Boron - Abstract
We have synthesized the first examples of radical-cation salts of BEDT-TTF with chiral borate anions, [B(malate)2](-), prepared from either enantiopure or racemic bidentate malate ligands. In the former case only one of two diastereoisomers of the borate anion is incorporated, while for the hydrated racemic salt one racemic pair of borate anions containing a R and a S malate ligand is incorporated. Their conducting and magnetic properties are reported. The tight-binding band calculation indicates that the chiral salt has an effective half-filled flat band, which is likely to be caused by the chiral structural feature.
- Published
- 2016
50. Self-Assembling Aryl-Naphthalendiimide Derivatives with a Nitroxide Radical
- Author
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Hiroki Akutsu, Shin'ichi Nakatsuji, Ayumi Kojoh, Makoto Karakawa, Jun-ichi Yamada, Kazunori Aoki, and Yoshio Aso
- Subjects
chemistry.chemical_compound ,Nitroxide mediated radical polymerization ,chemistry ,Aryl ,Radical ,Organic Chemistry ,Polymer chemistry ,Self assembling ,Self-assembly ,Crystal structure ,Photochemistry ,Charge-transfer complex ,Nitroxide radical - Abstract
A series of aryl-substituted naphthalenediimide derivatives that contain nitroxide radicals were prepared and their crystal structures were elucidated. Much stronger charge-transfer interactions were present in the derivatives with perfluorobenzene substituents than those with phenyl or 4-fluorophenyl substituents. These interactions result in the formation of single-component charge-transfer complexes by self-assembly of the naphthalenediimide derivatives to provide black crystals. As a consequence, the naphthalenediimide derivatives with perfluorobenzene substituents have better field-effect transistor (FET) properties than the other derivatives.
- Published
- 2012
- Full Text
- View/download PDF
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