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A new bromo-bridged Ni III compound has been synthesized. This compound displayed a strong antiferromagnetic interaction between spins located on Ni III species (J=(2350+/-500) K) that result from the strong covalency of the Ni--Br bond and the spin-Peierls transition below 150 K. This was shown by the results of magnetic susceptibility and 81Br nuclear quadrupole resonance spectroscopy analysis. We succeeded in the electrostatic carrier doping of a single crystalline sample by using a field-effect transistor device. This compound also showed n-type semiconductor behavior, which can be reasonably rationalized by the existence of a small amount of Ni II impurities.

The pressure response of the second-order Raman G' band of bundled double- (DWCNTs) and single-wall carbon nanotubes (SWCNTs) has been investigated by means of Raman spectroscopy using the 632.8 nm excitation. The different pressure responses of the G' peak in SWCNTs and its corresponding components associated with the inner and the outer tubes in DWCNTs can be attributed to the different diameters of the resonantly probed tubes and the strength of the inner-outer tube interaction.

Electric double layer field-effect transistors (EDL-FETs) of rubrene single crystals using a liquid polymer electrolyte were studied in a four-probe configuration. The channel sheet resistance and the contact resistance normalized by the contact width were 0.24 MΩ and 0.83 kΩ cm in the ON-state, respectively. These values are smaller than those of previously reported conventional rubrene crystal FETs, corroborating the high carrier density accumulation in the EDL-FET. In addition, peculiar peak behaviour in the transfer characteristics did not appear in the gate voltage dependence of four-probe conductivity. This observation leads us to conclude that the peak is ascribed to the increase of the contact resistance in the high gate voltage region.

The first ambipolar light-emitting transistor of an organic molecular semiconductor single crystal, tetracene, is demonstrated. In the device configuration, electrons and holes injected from separate magnesium and gold electrodes recombined radiatively within the channel. By varying the applied voltages, the position of the recombination/emission zone could be moved to any position along the channel. Because of the changes made to the device structure, including the use of single crystals and polymer dielectric layers and the adoption of an inert-atmosphere fabrication process, the set of materials that can be used for light-emitting transistors has been expanded to include monomeric molecular semiconductors.

Rhodococcus opacus strain B-4, which has recently been isolated as an organic solvent-tolerant bacterium, has a high hydrophobicity and exhibits a high affinity for hydrocarbons. This bacterium was able to survive for at least 5 days in organic solvents, including n-tetradecane, oleyl alcohol, and bis(2-ethylhexyl) phthalate (BEHP), which contained water less than 1% (w/v). The biocatalytic ability of R. opacus B-4 was demonstrated in the essentially nonaqueous BEHP using indigo production from indole as a model conversion. By the catabolism of oleic acid for NADH regeneration, indigo production increased up to 71.6 microg ml(-1) by 24 h.

We carried out77Se NMR measurements on BETS2(Cl2TCNQ) under pressure in order to investigate the magnetic properties of the insulating state which appears above 0.6 GPa. The relaxation rate 1/T1 at 0.7 GPa shows small peak-like anomaly at 20 K, indicating a spin density wave transition as observed in BETS2(Br2TCNQ).

In this work, individual single-wall carbon nanotubes (i-SWCNTs) and their parent bundled material (b-SWCNTs) are investigated by means of high pressure Raman spectroscopy. Pressure application results in the broadening and intensity redistribution of the radial breathing modes (RBMs) in both materials. These changes are more pronounced in the case of bundled SWCNTs as it is also evident by the abrupt increase of the G + bandwidth at ∼5.5 GPa, in contrast to the smoother pressure response of the individual tubes. Our experimental findings reflect the size dependent cross-section deformation of carbon nanotubes which evolves differently in the two materials investigated.

Electrical switching to multiple novel metastable states in a correlated two-dimensional crystal., Scaling down materials to an atomic-layer level produces rich physical and chemical properties as exemplified in various two-dimensional (2D) crystals including graphene, transition metal dichalcogenides, and black phosphorus. This is caused by the dramatic modification of electronic band structures. In such reduced dimensions, the electron correlation effects are also expected to be significantly changed from bulk systems. However, there are few attempts to realize novel phenomena in correlated 2D crystals. We report memristive phase switching in nano-thick crystals of 1T-type tantalum disulfide (1T-TaS2), a first-order phase transition system. The ordering kinetics of the phase transition were found to become extremely slow as the thickness is reduced, resulting in an emergence of metastable states. Furthermore, we realized unprecedented memristive switching to multistep nonvolatile states by applying an in-plane electric field. The reduction of thickness is essential to achieve such nonvolatile electrical switching behavior. The thinning-induced slow kinetics possibly make the various metastable states robust and consequently realize the nonvolatile memory operation. The present result indicates that a 2D crystal with correlated electrons is a novel nano-system to explore and functionalize multiple metastable states that are inaccessible in its bulk form.

We demonstrate electrical control of ferromagnetism in field-effect transistors with a trilayer quantum well (QW) channel containing an ultrathin n-type ferromagnetic semiconductor $(\mathrm{In},\mathrm{Fe})\mathrm{As}$ layer. A gate voltage is applied to control the electron wave functions ${\ensuremath{\varphi}}_{i}$ in the QW, such that the overlap of ${\ensuremath{\varphi}}_{i}$ and the $(\mathrm{In},\mathrm{Fe})\mathrm{As}$ layer is modified. The Curie temperature is largely changed by 42%, whereas the change in sheet carrier concentration is two to three orders of magnitude smaller than that of previous gating experiments. This result provides an approach for versatile, low power, and ultrafast manipulation of magnetization.

Magnetic skyrmions, swirling nanometric spin textures, have been attracting increasing attention by virtue of their potential applications for future memory technology and their emergent electromagnetism. Despite a variety of theoretical proposals oriented towards skyrmion-based electronics (that is, skyrmionics), few experiments have succeeded in creating, deleting and transferring skyrmions, and the manipulation methodologies have thus far remained limited to electric, magnetic and thermal stimuli. Here, we demonstrate a new approach for skyrmion phase control based on a mechanical stress. By continuously scanning uniaxial stress at low temperatures, we can create and annihilate a skyrmion crystal in a prototypical chiral magnet MnSi. The critical stress is merely several tens of MPa, which is easily accessible using the tip of a conventional cantilever. The present results offer a new guideline even for single skyrmion control that requires neither electric nor magnetic biases and consumes extremely little energy., Chiral magnets can support particle-like magnetization textures called skyrmions which form in lattices and can be manipulated for potential device applications. Here, the authors demonstrate the controlled creation and annihilation of a skyrmion lattice in MnSi single crystals using mechanical stress.

The second harmonic generation (SHG) produced from two-dimensional atomic crystals have been utilized recently in studying the grain boundaries and electronic structure of such ultra-thin materials. However, the SHG in many of these crystals, such as transition metal dichalcogenides (TMDCs), only occur in odd numbered layers with limited intensity due to their noncentrosymmetric nature. Here, we probe the SHG from the bulk noncentrosymmetric molybdenum disulfide (MoS2). Whereas the commonly studied 2H crystal phase’s anti-parallel nonlinear dipoles in adjacent layers give an oscillatory SH response, the parallel nonlinear dipoles of each atomic layer in the 3R phase constructively interfere to amplify the nonlinear light. Due to this interference, we observed the atomically phase-matched condition yielding a quadratic dependence between the intensity and layer number. Additionally, we probed the layer evolution of the A and B excitonic transitions in 3R-MoS2 using SHG spectroscopy and found distinct electronic structure differences arising from the crystal geometry. These findings demonstrate the dramatic effect of the symmetry and layer stacking of these atomic crystals.

We previously discovered multiple superconducting phases in the ammoniated Na-doped FeSe material, (NH3)yNaxFeSe. To clarify the origin of the multiple superconducting phases, the variation of Tc was fully investigated as a function of x in (NH3)yNaxFeSe. The 32 K superconducting phase is mainly produced in the low-x region below 0.4, while only a single phase is observed at x = 1.1, with Tc = 45 K, showing that the Tc depends significantly on x, but it changes discontinuously with x. The crystal structure of (NH3)yNaxFeSe does not change as x increases up to 1.1, i.e., the space group of I4/mmm. The lattice constants, a and c, of the low-Tc phase (Tc = 32.5 K) are 3.9120(9) and 14.145(8) Å, respectively, while a = 3.8266(7) Å and c = 17.565(9) Å for the high-Tc phase (~46 K). The c increases in the high Tc phase, implying that the Tc is directly related to c. In (NH3)yLixFeSe material, the Tc varies continuously within the range of 39 to 44 K with changing x. Thus, the behavior of Tc is different from that of (NH3)yNaxFeSe. The difference may be due to the difference in the sites that the Na and Li occupy.

Functionalities of two-dimensional (2D) crystals based on semiconducting transition metal dichalcogenides (TMDs) have now stemmed from simple field effect transistors (FETs) to a variety of electronic and opto-valleytronic devices and even to superconductivity. Among them, superconductivity is the least studied property in TMDs due to methodological difficulty accessing it in different TMD species. Here, we report the systematic study of superconductivity in MoSe2, MoTe2 and WS2 by ionic gating in different regimes. Electrostatic gating using ionic liquid was able to induce superconductivity in MoSe2 but not in MoTe2 because of inefficient electron accumulation limited by electronic band alignment. Alternative gating using KClO4/polyethylene glycol enabled a crossover from surface doping to bulk doping, which induced superconductivities in MoTe2 and WS2 electrochemically. These new varieties greatly enriched the TMD superconductor families and unveiled critical methodology to expand the capability of ionic gating to other materials.

Symmetry-breaking has been known to play a key role in noncentrosymmetric superconductors with strong spin-orbit-interaction (SOI). The studies, however, have been so far mainly focused on a particular type of SOI, known as Rashba SOI, whereby the electron spin is locked to its momentum at a right-angle, thereby leading to an in-planar helical spin texture. Here we discuss electric-field-induced superconductivity in molybdenum disulphide (MoS2), which exhibits a fundamentally different type of intrinsic SOI manifested by an out-of-plane Zeeman-type spin polarization of energy valleys. We find an upper critical field of approximately 52 T at 1.5 K, which indicates an enhancement of the Pauli limit by a factor of four as compared to that in centrosymmetric conventional superconductors. Using realistic tight-binding calculations, we reveal that this unusual behaviour is due to an inter-valley pairing that is symmetrically protected by Zeeman-type spin-valley locking against external magnetic fields. Our study sheds a new light on the interplay of inversion asymmetry with SOI in confined geometries, and its unprecedented role in superconductivity., 37 pages, 11 figures, http://meetings.aps.org/Meeting/MAR15/Session/G11.11

Electrostatic modification of functional materials by electrolytic gating has demonstrated a remarkably wide range of density modulation, a condition crucial for developing novel electronic phases in systems ranging from complex oxides to layered chalcogenides. Yet little is known microscopically when carriers are modulated in electrolyte-gated electric double-layer transistors (EDLTs) due to the technical challenge of imaging the buried electrolyte-semiconductor interface. Here, we demonstrate the real-space mapping of the channel conductance in ZnO EDLTs using a cryogenic microwave impedance microscope. A spin-coated ionic gel layer with typical thicknesses below 50 nm allows us to perform high resolution (on the order of 100 nm) sub-surface imaging, while maintaining the capability of inducing the metal-insulator transition under a gate bias. The microwave images vividly show the spatial evolution of channel conductance and its local fluctuations through the transition, as well as the uneven conductance distribution established by a large source-drain bias. The unique combination of ultra-thin ion-gel gating and microwave imaging offers a new opportunity to study the local transport and mesoscopic electronic properties in EDLTs., to be published on Nano Letter

High-mobility short-channel organic thin-film transistors fabricated using a dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]-thio--phene (DNTT) precursor (5,14-N--phenylmaleimide DNTT, endo-isomer-rich fraction) and polystyrene (PS) blends are reported. The DNTT grains are "single-crystal"-like and the field-effect mobility of the devices ranges up to 4.7 cm(2) V(-1) s(-1). The PS layer functions as a hydrophobic passivation layer on the Si/SiO2 substrate.

Electrically driven organic lasers are among the best lasing devices due to their rich variety of emission colors as well as other advantages, including printability, flexibility and stretchability. However, electrically driven lasing in organic materials has not yet been demonstrated because of serious luminescent efficiency roll-off under high current density. Recently, we found that the organic ambipolar single-crystal transistor is an excellent candidate for lasing devices because it exhibits less efficient roll-off, high current density and high luminescent efficiency. Although a single-mode resonator combined with light-emitting transistors (LETs) is necessary for electrically driven lasing devices, the fragility of organic crystals has strictly limited the fabrication of resonators and LETs with optical cavities have never been fabricated until now. To achieve this goal, we improved the soft ultraviolet-nanoimprint lithography method and demonstrated electroluminescence from a single-crystal LET with a grating resonator, which is a crucial milestone for future organic lasers.

A superconductivity dome is created by the electronic structure of the molecular building block of an unconventional superconductor., Understanding the relationship between the superconducting, the neighboring insulating, and the normal metallic state above Tc is a major challenge for all unconventional superconductors. The molecular A3C60 fulleride superconductors have a parent antiferromagnetic insulator in common with the atom-based cuprates, but here, the C603– electronic structure controls the geometry and spin state of the structural building unit via the on-molecule Jahn-Teller effect. We identify the Jahn-Teller metal as a fluctuating microscopically heterogeneous coexistence of both localized Jahn-Teller–active and itinerant electrons that connects the insulating and superconducting states of fullerides. The balance between these molecular and extended lattice features of the electrons at the Fermi level gives a dome-shaped variation of Tc with interfulleride separation, demonstrating molecular electronic structure control of superconductivity.

Rare-earth-metal-doped fullerides with a nominal composition of R 3 C 70 (R = Sm, Eu, Yb) adopt a pseudomonoclinic structure in which C 70 dimers glued with rare-earth ions are involved. High-temperature powder X-ray diffraction experiments revealed that the dimers undergo reversible first-order structural phase transitions, associated with reduction of the unit cell volume, similar to the results observed in previous high-pressure experiments. Structural analyses showed that C 70 molecules are realigned to form closely packed structures, causing a reduction of volume at high temperature. The derived charge density map indicates that the transitions can be regarded as reversible structural changes from fullerene dimers to monomers. These features are ascribed to the unique bonding nature of rare-earth C 70 compounds.

Reactions of K 1.62 [Pt(ox) 2 ]·2H 2 O and [Cu(bpy)(H 2 O) 3 ](NO 3 ) 2 yielded partially oxidized one-dimensional (1D) bis-(oxalato)platinates of [Cu(bpy)(H 2 O)n] 6 [Pt(ox) 2 ] 7 ·7H 2 O (n = 2, 3, or 4) (1) and [Cu(bpy)(H 2 O) n ] 8 [Pt(ox) 2 ] 10 ·8H 2 O (n = 3 or 4) (2). The average oxidation numbers of the platinum ions in 1 and 2 are +2.29 and +2.40, respectively. Complexes 1 and 2 crystallize in the triclinic P1 and monoclinic C2/c space groups, respectively, and the [Pt(ox) 2 ] n- anions are stacked along the crystallographic b axis with 7-fold periodicity for 1 and 10-fold periodicity for 2. In 1, an oxalato ligand in the platinum chain directly coordinates to a paramagnetic [Cu(bpy)(H 2 O) 3 ] 2+ ion, whereas no such direct coordination was observed for 2. The electrical conductivity of 2 at room temperature along the platinum chain is approximately 3 orders of magnitude smaller (σ ∥ = 1.3 x 10 -3 S cm -1 ) than that of 1 (σ ∥ = 0.9-0.5 S cm -1 ), and the activation energies of 1 and 2 are 29 and 67 meV, respectively. The longest inter-platinum distances in 1 and 2 are 2.762 and 3.0082 A, respectively, and this is responsible for the lower electrical conductivity of 2. An X-ray oscillation photograph taken along the b axis of 1 reveals the 7-fold periodicity in the 1D chain, consistent with the period of the Peierls distortion estimated from the degree of partial oxidation. The semiconducting state of 1 can therefore be regarded as a commensurate Peierls state. The magnetoresistance of 1 at ambient pressure indicates no interaction between conduction electrons in the platinum chain and local spins of the paramagnetic Cu" ions. Application of hydrostatic pressures of up to 3 GPa enhances electrical conduction, as is often seen as the usual pressure effect on the electrical conductivity, which is due to enhanced orbital (Pt-5d/) overlap by pressure application.

Ge1−xCrx films grown by MBE show quite large magneto-transport effects in the temperature range up to the room temperature. Especially, Hall resistance in DC- fields up to 10 Tesla and magneto-resistances in pulsed fields up to 60 Tesla show significant nonlinear field dependence. The magnetic field effects on the transport properties are usually quite small in conducting materials and phonon plays main role above liq. N2 temperature. ESR measurements suggest that antiferromagnetism up to TNaround 70 K exists and the critical spin fluctuation might affects to the nonlinear field dependence in magneto-transport phenomena in high temperatures.

Effects of Interface modification on the organic single crystal transistors have been investigated using self-assembled monolayers and double gate configurations. Systematic carrier density control associated with the shift of Vth was achieved by the polarized self-assembled monolayers fabricated in between the gate oxide and organic single crystals, and by the second gate electrode, which was fabricated on the other side of the primary gate electrode.

We have synthesized single phase samples of Li-doped ZrNCl and investigated the superconducting properties of them. Especially, we have measured the specific heat of Li0.12ZrNCl sample with T c = 12.7 K . It has been revealed that this material has a small Sommerfeld constant γ = 1.0 ± 0.1 mJ / mol K 2 . In addition, the dual nature of coupling strength has also been unveiled.: While electron–phonon coupling constant λ is estimated to be less than 0.22, superconducting gap ratio and specific heat jump at Tc indicate intermediate to strong coupling of the present superconductor.

Physical properties of a new superconductor Ba 24 Si 100 crystallographically identical to Ba 24 Ge 100 are studied by electric transport, specific heat capacity and magnetic susceptibility measurements. The density of states at the Fermi level N EF =0.148 states eV −1 (Si-atom) −1 and a discrete jump of C p at the superconducting transition temperature Δ C p =0.272 J K −1 mol −1 are obtained. The exponential fit of C p under the superconducting states gives an energy gap 2 Δ =0.423 meV and shows that this is a superconductor having an s-wave character or an isotropic energy gap. On the basis of the experimental data, other important physical parameters are also described.

Raman spectroscopy has been employed in the study of the high pressure response of metallic single-(SWCNTs) and double-wall carbon nanotubes (DWCNTs). Besides a variety of pressure induced changes, such as the deformation of SWCNTs and the DWCNT outer tubes, as well as the quasi-isolation of the inner tubes, a narrowing of the characteristic Breit–Wigner–Fano Raman peak is also observed. As the width and asymmetry of this peak reflects the coupling of the vibrational mode to an electronic continuum, its pressure induced narrowing can be ascribed to a decoupling process, possibly connected to the enhanced tube–tube interaction and the deformation of the tubes at elevated pressures.

We report on the first synthesis of Li-intercalated manganese-phthalocyanine (MnPc) in the bulk form and on the evolution of the structural and magnetic properties as a function of Li concentration, x. We find that solid beta-MnPc, which comprises rodlike assemblies of individual planar molecules, is best described as a glassy one-dimensional ferromagnet without three-dimensional ordering and that it can be quasi-continuously intercalated with Li up to x = 4, forming an isosymmetrical series of Li(x)[MnPc] phases. Inserted Li+ ions strongly bond to pyrrole-bridging nitrogen atoms of the Pc rings, thereby disrupting the ferromagnetic Mn-N(a)...Mn superexchange pathways. This gradually induces a crossover of the intrachain exchange interactions from ferromagnetic to antiferromagnetic as the doping level, x, increases coupled with a spin-state transition of the Mn2+ ions from intermediate spin, S = 3/2, to high spin, S = 5/2.

We observed an ambipolar behavior in multiwalled carbon nanotubes (MWNT) in a back-gate configuration, which allowed us to perform systematic inspection of the low-temperature transport properties against gate voltage. Power-law behaviors in temperature and bias-dependent conductance, disappeared when a high gate voltage was applied, and conductance became temperature- and bias independent. This indicates a gate-induced transformation from the unconventional to the normal metallic states in MWNT.

Pressure dependence of T c , lattice constant, and phonon frequency has been investigated for layered nitride superconductors, Li 0.5 (THF) y HfNCl and ZrNCl 0.7 . Analysis based on McMillan’s theory has revealed that the electron–phonon coupling constant λ is larger than 3, and that the relevant phonon is of low frequency around 100 cm −1 . The anomalously large value of λ is in sharp contrast with previous theories and an experiment.

We observed an ambipolar behavior in multiwalled carbon nanotubes (MWNT) in a back‐gate configuration. The four‐terminal measurement indicates that the ambipolar behavior is originated from an intrinsic conductivity of MWNT. power‐law behaviors, in temperature‐ and bias‐dependent conductance, disappeared when a high gate voltage is applied, and conductance become temperature‐ and bias‐independent. This result indicates an occurrence of gate‐induced transformation from the unconventional to the normal metallic states in MWNT.

We report a $^{11}$B NMR line shape and spin-lattice relaxation rate ($1/(T_1T)$) study of pure and lightly carbon doped MgB$_{2-x}$C$_{x}$ for $x=0$, 0.02, and 0.04, in the vortex state and in magnetic field of 23.5 kOe. We show that while pure MgB$_2$ exhibits the magnetic field distribution from superposition of the normal and the Abrikosov state, slight replacement of boron with carbon unveils the magnetic field distribution of the pure Abrikosov state. This indicates a considerable increase of $H_{c2}^c$ with carbon doping with respect to pure MgB$_2$. The spin-lattice relaxation rate $1/(T_1T)$ demonstrates clearly the presence of a coherence peak right below $T_c$ in pure MgB$_2$, followed by a typical BCS decrease on cooling. However, at temperatures lower than $\approx 10$K strong deviation from the BCS behavior is observed, probably from residual contribution of the vortex dynamics. In the carbon doped systems both the coherence peak and the BCS temperature dependence of $1/(T_1T)$ weaken, an effect attributed to the gradual shrinking of the $\sigma $ hole cylinders of the Fermi surface with electron doping., Comment: 8 pages, 6 figures, submitted to Phys. Rev. B

We report the fabrication of thin film SWNT‐FETs using a novel and simple solution process methodology. The SWNTs are dispersed in an organic solution in a narrow bundle structure and form nonaligned arrays which become the channels of FETs. The thin film FETs operate even at low temperature, and have the mobility that is about 100 times greater than those of other solution‐processed organic thin film FETs. This simple fabrication process will help develop a novel route for the large‐scale liquid phase production of commercially available flexible organic devices.

We measured third-order nonlinear susceptibility (χ(3)) spectra in semiconducting single-walled carbon nanotubes (SWNTs) by the Z-scan method. |Im χ(3)| is remarkably enhanced under resonant excitation to the lowest interband transition, reaching 4.2 × 10−6 esu. A comparison of the transient absorption changes evaluated by degenerate and nondegenerate pump-probe measurements suggests that the resonant enhancement of |Im χ(3)| is dominated by a coherent process rather than by incoherent one such as saturation of absorption.

Heat capacities of single crystals of Fe x NbS 2 ( x =0.159, 0.281, 0.309 and 0.325) were measured at temperatures from 1.8 to 100 K. Heat capacity anomalies were observed in all of the single crystals. Both Fe 0.325 NbS 2 and Fe 0.309 NbS 2 underwent the successive three magnetic phase transitions around 40 K. The successive phase transitions originate in the √3 a ×√3 a superstructure in-plane of Fe 1/3 NbS 2 . A phase diagram of Fe x NbS 2 system was established from the obtained temperatures of magnetic phase transition and spin-glass like transition.

Electronic properties of the major and minor isomers of Pr@C 82 , I (C 2v ) and II (C s ), are studied by Raman scattering, resistivity measurement, scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). The valences of the Pr atom in both isomers are determined to be +3 based on the Raman shift in the Pr–C 82 stretching mode. The transport properties showed that both isomers are normal semiconductors with a small energy gap ( E g ). STM of isomer I shows internal structures dependent on bias voltage V s , and STS shows that this isomer is a semiconductor with E g = 0.7 eV.

Characteristics of aggregated single-walled carbon nanotube (SWNT) as a channel of field effect transistors (FETs) were examined. SWNTs were dispersed in a solution of dimethylformamide in a narrow bundle structure to form non-aligned arrays, which became channels of FETs. The network-SWNT-FETs produced in this solution process was found to have a mobility of 10.9 cm2/V s, ≈100 times as high as those reported for other solution-processed organic thin-film FETs formed by solution processes, and the present product exhibited the ambipolar character observed in individual-SWNT-FETs.

A novel approach to develop a peptide, that can recognize fullerene (C60) is described for affinity selection of phage displayed peptides from a combinatorial peptide library. Biopanning was performed using cyclic 7-mer peptide library against C60 films deposited on silicon (Si) substrate, and eluted phages with organic solvent. The phage, that recognized C60 films deposited on Si substrate, were obtained from biopanning. The nucleotides of the phage, coding a cyclic 7-mer peptide, were sequenced by standard method. Seventeen kinds of peptide displayed phages were obtained. One kind of peptide (peptide No. 4) displayed phage recognized the C60 films deposited on Si substrate. Peptide No. 4 displayed no affinity towards the Si substrate. The recognition event was monitored by a fluorescent immunoassay. Additionally, peptide No. 4 phage could recognize C60 in powder form, but not the graphite powder. This recognition event in powder form was also observed by a fluorescent immunoassay.

X-ray diffractions and electronic transports for the Ce@C82 isomers I and II, which refer to major and minor isomers, respectively, are studied in a wide temperature region to clarify the structura...

The magnetism on (Ga,Mn)N with high-TC is investigated and the ferromagnetic magnetization process is discussed in comparison with the superparamagnetism in the segregation model. Transport experiments were made in steady magnetic fields up to 27 T. The results show the close relation between spontaneous magnetization and carrier density. The anisotropy in magnetoresistance shows anomalous field dependence and suggests existence of some nonmagnetic origin.

Temperature and magnetic field dependences of the anomalous Hall effect have been investigated for single crystals of Mo-based ferromagnets with pyrochlore structure. The Hall resistivity of Nd2Mo2O7 compound shows unconventional temperature dependence whereas Gd2Mo2O7 exhibits rather normal behaviour. The Berry phase model can explain the difference well; it is attributed to the difference in nature of the anisotropy of the rare-earth moment and the resultant Mo spin state. The Hall resistivity of Nd2Mo2O7 changes its sign with increasing field applied along the [111] direction, while it monotonically approaches zero with the field applied along the [100] or [110] direction. This behaviour is also in accord with the prediction of the Berry phase theory.

Pentacene is a well known organic semiconductor because of its high mobility in the field-effect transistor devices, and also because film conductivity can be dramatically increased by electron and hole doping. For chemical and structural identification of the conducting phase, we carried out an intercalation experiment of pentacene with iodine at various iodine/pentacene ratios. X-ray powder diffraction measurements revealed that there are two stable phases with different iodine concentrations. In the intermediate intercalation phase with the concentration of (pentacene)I2 and high conductivity, I3− ions are inserted between the neighboring layers of pentacene. The saturation phase with higher iodine concentration is formed mainly of I5−, associated with a significant lattice expansion.

We study the effect of carbon doping on the Raman spectrum of the MgB 2 superconductor. Out data show that significant changes in the Raman spectra of the MgB 2− x C x compounds occur for carbon concentrations x >0.04. The E 2g mode at ∼580 cm −1 hardens only moderately upon increased doping despite direct carbon substitution in the boron layers, while the dependence of its full width at half maximum (FWHM) on x reveals the competing effects of reduced electron–phonon coupling and increased disorder. The results are discussed in the framework of anisotropic lattice contraction and the position of the σ sub-bands with respect to the Fermi energy level. The relative intensity of the phonon peak at ∼770 cm −1 , associated with a peak in the phonon density of states, increases considerably and dominates for x =0.08. Additionally, it hardens and broadens with increasing x in the range 0.04–0.08. These changes can be associated with carbon substitution-induced disorder in the investigated samples.

This article reviews the current status of chemically doped fullerene superconductors and related compounds, with particular focus on Mott–Hubbard states and the role of molecular orbital degeneracy. Alkaline-earth metal fullerides produce superconductors of several kinds, all of which have states with higher valence than (C60)6−, where the second lowest unoccupied molecular orbital (the LUMO + 1 state) is filled. Alkali-metal-doped fullerides, on the other hand, afford superconductors only at the stoichiometry A3C60 (A denotes alkali metal) and in basically fcc structures. The metallicity and superconductivity of A3C60 compounds are destroyed either by reduction of the crystal symmetry or by change in the valence of C60. This difference is attributed to the narrower bandwidth in the A3C60 system, causing electronic instability in Jahn–Teller insulators and Mott–Hubbard insulators. The latter metal–insulator transition is driven by intercalation of ammonia molecules into A3C60-type superconductors. Furthermore, the triple degeneracy of the LUMO state of C60 plays a crucial role in the metal–insulator transition and in controlling the magnetic structures of insulating states, possibly providing novel properties of degenerate orbitals. The goal of this article is to establish a unifying picture of fullerene intercalation compounds, and to clarify the underlying physics: competing energy scales and orbital properties of molecule-based systems.

The superconducting properties of MgB 1.96 C 0.04 have been investigated by the transverse-field muon spin rotation (TF-μSR) technique. The extracted temperature dependence of the μ + spin depolarization rate, σ at TF=0.6 T has been analyzed in terms of a two-gap model. Carbon doping affects the size of both superconducting gaps and the doping effect is more pronounced for the smaller gap, which is related to the 3D π-sheets of the Fermi surface. The ‘universal’ correlation between the superconducting transition temperature, T c and the effective Fermi temperature, T F (Uemura plot) is also discussed.

High pressure Raman scattering was used to probe the pressure response of the two-dimensional tetragonal and rhombohedral C 60 polymers. The phonon frequencies as a function of pressure for the various Raman modes of the polymeric phases show a slope change near ∼4 GPa. As pressure increases above 4 GPa, the pressure coefficients for the majority of the modes exhibit reversible change to lower values. These changes may be attributed to a possible structural modification of the polymers from their initial state, which is characterized by highly anisotropic intermolecular interactions (strong in-plane covalent bonds and weak out-of-plane van der Waals interactions), to a more isotropic one upon application of the external pressure. This behavior is a common theme of other fullerene materials displaying bonding anisotropy.

Intercalation of C(70) with europium affords two kinds of magnetic compounds, a canted antiferromagnet Eu(x)C(70) (x approximately 3) and a ferromagnet Eu(x)C(70) (x approximately 9) with transition temperatures (T(C)) of 5 and 38 K, respectively. The Curie constants in the paramagnetic phase and the saturation moment in the ferromagnetic phase are both understood by the full moment of Eu(2+) for both systems. The structure of Eu(3)(-)(delta)C(70) (delta approximately 0.27) is pseudo-monoclinic, derived by a simple deformation of the parent face-centered cubic (fcc) structure. Eu(9)(-)(delta)C(70) (delta approximately 0.2) forms an fcc structure, in which cuboctahedral clustering of Eu(2+) ions is observed in the enhanced size octahedral holes. The observed T(C) of the Eu(9)(-)(delta)C(70) ferromagnet is comparable to or larger than those of simple binary Eu-based ferromagnets, such as Eu chalcogenides or carbides, despite the low atomic ratio of Eu in the chemical formulas. This can be understood by the short Eu(2+)-Eu(2+) distances and high coordination numbers permitted by the multiple occupation by Eu(2+) ions of the expanded octahedral interstitial sites in higher fullerene-based solids.