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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

The electronic properties of molecular conductors can be readily varied via physical or chemical pressure as it enlarges the bandwidth W. This enables them to cross the Mott insulator-to-metal phase transition by reducing electronic correlations U/W. Here we introduce an alternative path by spatially expanding the molecular orbitals when partially replacing sulfur by selenium in the constituting bis-(ethylenedithio)-tetrathiafulvalene (BEDT-TTF) molecules of the title compound. We characterize how the insulating quantum-spin-liquid state is tuned via a Mott transition to the metallic Fermi-liquid state crossing a narrow region of superconductivity. The transport, dielectric, and optical measurements reveal that at this first-order phase transition, metallic regions coexist in the insulating matrix leading to pronounced percolative effects, which are most obvious in the strong enhancement of the dielectric constant at low temperatures.

The two-dimensional organic superconductor $\ensuremath{\lambda}\ensuremath{-}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ exhibits pronounced charge fluctuations below $T\ensuremath{\approx}150$ K, in contrast to the sibling compound $\ensuremath{\kappa}\ensuremath{-}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ that remains metallic down to milli-Kelvin. Infrared spectroscopy reveals only minor splitting in the vibrational features of the latter compound, common to other strongly dimerized $\ensuremath{\kappa}$-type salts. When the organic molecules are arranged in the $\ensuremath{\lambda}$-type pattern, however, a strong vibrational ${\ensuremath{\nu}}_{27}({b}_{1u})$ mode is present that forms a narrow doublet. Most important, when cooling $\ensuremath{\lambda}\ensuremath{-}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ below 150 K, two weak side modes appear due to charge disproportionation that amounts to $2\ensuremath{\delta}=0.14e$. In analogy to the ${\ensuremath{\beta}}^{\ensuremath{'}\ensuremath{'}}$-type organic conductors, we propose that charge fluctuations play an important role in emerging of unconventional superconductivity in $\ensuremath{\lambda}\ensuremath{-}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ at ${T}_{c}=4.7$ K. We discuss the possibility of a charge-density wave that coexists with the proposed spin-density-wave state.

Advanced manufacturing processes such as additive manufacturing offer now the capability to control material placement at unprecedented length scales and thereby dramatically open up the design space. This includes the considerations of new component topologies as well as the architecture of material within a topology offering new paths to creating lighter and more efficient structures. Topology optimization is an ideal tool for navigating this multiscale design problem and leveraging the capabilities of advanced manufacturing technologies. However, the resulting design problem is computationally challenging as very fine discretizations are needed to capture all micro-structural details. In this paper, a method based on reduction techniques is proposed to perform efficiently topology optimization at multiple scales. This method solves the design problem without length scale separation, i.e., without iterating between the two scales. Ergo, connectivity between space-varying micro-structures is naturally ensured. Several design problems for various types of micro-structural periodicity are performed to illustrate the method, including applications to infill patterns in additive manufacturing.

In this work, the thermodynamic properties of the organic superconductor $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ are investigated to study a high-field superconducting state known as the putative Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase. We observed a small thermodynamic anomaly in the field ${H}_{\mathrm{FFLO}}\phantom{\rule{4pt}{0ex}}\ensuremath{\sim}10$ T, which corresponds to the Pauli limiting field ${H}_{\mathrm{P}}$. This anomaly probably originates from a transition from a uniform superconducting state to the FFLO state. ${H}_{\mathrm{FFLO}}$ does not show a strong-field angular dependence due to a quasi-isotropic paramagnetic effect in $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$. The thermodynamic anomaly at ${H}_{\mathrm{FFLO}}$ is smeared out. and the low-temperature upper critical field ${H}_{\mathrm{c}2}$ changes significantly if fields are not parallel to the conducting plane, even for a deviation of $\ensuremath{\sim}0.{5}^{\ensuremath{\circ}}$. This behavior indicates that the high-field state is very unstable, as it is influenced by the strongly anisotropic orbital effect. Our results are consistent with the theoretical predictions on the FFLO state and show that the high-field superconductivity is probably an FFLO state in $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ from a thermodynamic point of view.

We performed $^{13}\mathrm{C}$ NMR measurements on an organic superconductor $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{B}\mathrm{E}\mathrm{T}\mathrm{S})}_{2}\mathrm{Ga}{\mathrm{Cl}}_{4}$ [BETS: bis(ethylenedithio)tetraselenafulvalene] to investigate the pressure effect on the spin density wave (SDW) fluctuations at low temperatures, which were observed at ambient pressure. We found that the spin-lattice relaxation rate divided by temperature $(1/{T}_{1}T)$ is significantly enhanced at low temperatures at 3 kbar, implying enhancement of the SDW fluctuation. When further pressure is applied, increase in $1/{T}_{1}T$ at low temperatures is suppressed and $1/{T}_{1}T$ becomes temperature independent, indicating the Fermi liquid state. Moreover, we revealed that the Korringa factor under pressure becomes double compared to its value at ambient pressure, suggesting a significant change in electron correlation. We discuss the effect of the SDW fluctuation and the electron correlation on the unconventional superconductivity.

We performed angular and temperature-dependent electron-spin-resonance measurements in the quasi-two-dimensional organic conductor $\ensuremath{\kappa}\text{\ensuremath{-}}{(\text{BEDT-TTF})}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{CN})}_{2}]\mathrm{I}$. The interlayer spin diffusion is much weaker compared to the Cl and Br analogs, which are antiferromagnetic insulator and paramagnetic metal, respectively; $\ensuremath{\kappa}\text{\ensuremath{-}}{(\text{BEDT-TTF})}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{CN})}_{2}]\mathrm{I}$ behaves insulating when cooled below $T=200\phantom{\rule{4pt}{0ex}}\mathrm{K}$. A spin gap ($\mathrm{\ensuremath{\Delta}}\ensuremath{\approx}18\phantom{\rule{4pt}{0ex}}\mathrm{K}$) opens at low temperatures leading to a spin-singlet state. Due to intrinsic disorder a substantial number of spins ($\ensuremath{\sim}1%$) remains unpaired. We observe additional signals below $T=4\phantom{\rule{4pt}{0ex}}\mathrm{K}$ with a pronounced anisotropy indicating the presence of local magnetic moments coupled to some fraction of those unpaired spins.

For the unconventional organic superconductor $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ [BETS = bis(ethylenedithio) tetraselenafulvalene], the importance of both spin and charge degrees of freedom has been discussed based on the broadening of the NMR linewidth due to charge disproportionation and the occurrence of a spin-density-wave phase near the superconducting phase. NMR with the nuclear spin of $1/2$, previously used for studying organic conductors, is an effective method for revealing electronic states microscopically; however, it cannot distinguish between charge and spin anomalies. To resolve this problem, in this paper, we performed $^{69,71}\mathrm{Ga}$-NMR measurements, which enabled us to study both charge and spin dynamics using different gyromagnetic ratios and quadrupole moments between two isotopes. The spin-lattice relaxation rate is dominated by electric-field gradient fluctuations originating from molecular dynamics above 150 K and, below this temperature, it is dominated by spin fluctuations derived from the $\ensuremath{\pi}$ electrons of BETS layers. This change in the relaxation mechanism is considered to be due to the development of interactions between ${\mathrm{GaCl}}_{4}$ ions and BETS layers upon freezing of the molecular motion by cooling. Below 150 K, the contribution of spin fluctuations monotonically increases, and no increase in the charge fluctuation was observed, suggesting that the spin degree of freedom plays a major role in low-temperature physical properties. Our findings will aid theoretical studies on superconducting properties.

We performed $^{13}\mathrm{C}$-NMR measurements on an organic superconductor $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ to investigate the superconducting (SC) gap symmetry, where BETS stands for bis(ethylenedithio)tetraselenafulvalene. As the temperature approaches 0 K, the Knight shift in the SC state decreases; the nuclear spin-lattice relaxation rate $1/{T}_{1}$ shows cubic temperature dependence below the SC transition temperature ${T}_{c}$ without a coherence peak. These results can be understood in terms of $d$-wave superconductivity. Moreover, an increase in $1/{T}_{1}T$ at lower temperatures was observed just above ${T}_{c}$; this behavior can be interpreted as an effect of spin-density-wave (SDW) fluctuation. We suggest that the $d$-wave superconductivity of $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ originates from SDW fluctuation.

This paper examines the determinants of corporate savings in a cross-country panel setting. Specifically, it employs firm-level data covering more than 540,000 firm-year observations for 12 advanced and emerging market economies. Panel regression results suggest that reductions in statutory corporate income tax rates can explain one-third of the rise in corporate savings (defined as net financial assets) in 2003-17. This finding is supported by a propensity scores matching analysis of the effects of changes in corporate income tax rates.

We have performed $^{13}\mathrm{C}$ NMR measurements on $\ensuremath{\lambda}\ensuremath{-}{(\mathrm{BEDT}\ensuremath{-}\mathrm{STF})}_{2}{\mathrm{FeCl}}_{4}$ to reveal the mechanism of unconventional paramagneticlike behavior observed in $\ensuremath{\lambda}$-type molecular $\ensuremath{\pi}\ensuremath{-}d$ systems. $^{13}\mathrm{C}$ NMR spectra and nuclear spin-lattice relaxation rate $1/{T}_{1}$ revealed that the $\ensuremath{\pi}$ and $3d$ electron systems undergo an antiferromagnetic transition simultaneously at 16 K with the assistance of the $\ensuremath{\pi}\ensuremath{-}d$ interaction. We found that the sublattice magnetizations of the $\ensuremath{\pi}$ and $3d$ spins show different temperature dependence below ${T}_{\mathrm{N}}$, which is derived from the magnetic coupling between the two sublattice systems with different magnetic natures. We discuss the relationship between the two different magnetization processes and the unconventional magnetic behavior in $\ensuremath{\lambda}$-type molecular $\ensuremath{\pi}\ensuremath{-}d$ system.

This paper identifies the electronic state just close to the superconducting phase in a system of organic conductors lambda-(BETS)2GaBrxCl4-x as a spin-density-wave state, using nuclear magnetic resonance and resistivity measurements. This finding explains the unexplainable enhancement of spin fluctuation at low temperatures in lambda-(BETS)2GaCl4 and suggests that the superconductivity of lambda-type salts is mediated by spin-density-wave fluctuations.

We consider a half-order time-fractional diffusion equation in an arbitrary dimension and investigate inverse problems of determining the source term or the diffusion coefficient from spatial data at an arbitrarily fixed time under some additional assumptions. We establish the stability estimate of Lipschitz type in the inverse problems and the proofs are based on the Bukhgeim-Klibanov method by using Carleman estimates., Comment: 26 pages

A family of organic conductors, α-(BEDT-TTF)2MHg(SCN)4, is known to show the density wave (DW) state for M = Tl, K, and Rb salts, or the superconducting (SC) state for M = NH4 salt at low temperatu...

Influences of coarse aggregate on the mechanical properties of Strain Hardening Cementitious Composite (SHCC) were experimentally investigated at the material and structural level. In the experiments, maximum size and volume fraction of coarse aggregate were varied as parameters. Direct uni-axial tensile tests and bending tests were carried out in order to evaluate the mechanical performance such as tensile strength and elongation capacity of SHCC itself. And also, bending-shear loading tests of steel reinforced SHCC (R/SHCC) beams were conducted. As the results, decreasing of tensile performances of SHCC in material level were observed by an increasing of the volume fraction of coarse aggregate. However, shear capacity of R/SHCC beam did not decrease. Both the tensile performance and the aggregate interlocking has effect on the mechanical behavior of R/SHCC beam failed in diagonal shear. It was suggested that these two mechanisms are the trade-off relation and the aggregate interlocking had significant effect on the shear capacity in this study., This is an accepted version of the article presented at Strain-Hardening Cement-Based Composites, RILEM Bookseries 15, DOI 10.1007/978-94-024-1194-2_16., 4th International Conference on Strain-Hardening Cement-Based Composites (SHCC4) From 18 September 2017 to 20 September 2017 Dresden, Germany

We consider the first and half order time fractional equation with the zero initial condition. We investigate an inverse source problem of determining the time-independent source factor by the data at an arbitrarily fixed time and we establish the conditional stability estimate of H\"older type in our inverse problem. Our method is based on the Bukhgeim-Klibanov method by means of the Carleman estimate. We also derive the Carleman estimate for the first and half order time fractional diffusion equation., Comment: 19 pages