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We consider inverse problems for the first- and half-order time-fractional equation. We establish the stability estimates of Lipschitz type in inverse source and inverse coefficient problems by means of the Carleman estimates. [ABSTRACT FROM AUTHOR]

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 in-plane (azimuthal angle) anisotropic features in the superconducting electronic heat capacity Cele. The polar angle (θ) dependences of Cele have a simple twofold periodicity caused by the anisotropy of the critical field Hc2. In contrast, the azimuthal angle (ϕ) dependences show asymmetric anisotropies including twofold and fourfold-like terms originating from the anisotropy of the superconducting gap function. From the results, we discuss the gap function from the perspective of the mixed symmetry caused by the antiferromagnetic spin fluctuation on the low-symmetry λ-type lattice. [ABSTRACT FROM AUTHOR]

Low-temperature heat capacity of the organic superconductor λ-(BETS)2GaCl4 in a temperature range between 0.6 and 10K was measured for a single crystal sample by relaxation calorimetry technique. The contribution of electronic heat capacity in the superconducting state shows T2 dependence at lower temperature that indicates the existence of quasi-particle excitations from the line-nodal gap structure of d-wave pairing. The recovery of the electronic heat capacity coefficient, γ by magnetic field shows H1/2 dependence that is consistent with the picture of line-nodal superconductor. In spite of the different packing from typical organic superconductors κ-(BEDT-TTF)2X, the λ-type BETS salt also shows a feature of d-wave symmetry pairing. [ABSTRACT FROM AUTHOR]

We present experimental evidence for the charge fluctuation in the spin-liquid candidate κ-(BEDT-TTF)2Cu2(CN)3. The temperature and pressure dependence of the Raman spectrum in the region of 1300-1600 cm-1 were measured. The charge-sensitive ν2 mode at 1500 cm-1 exhibited a linewidth broadening below 60K when the sample was slowly cooled. This broadening is induced by a structural change (increase in interdimer transfer integrals). The hydrostatic pressure significantly suppressed the broadening in the metallic phase. This result indicates that the linewidth broadening originates from the valence (charge) fluctuation within the BEDT-TTF dimer, because the screening effect suppresses the interdimer Coulomb interaction that causes the charge disproportionation. The line shape was analyzed using the fast fluctuating model and slow or static inhomogeneous model. [ABSTRACT FROM AUTHOR]

We performed tunneling spectroscopy (STS) measurement in an organic superconductor, partially deuterated κ-(BEDT-TTF-d[3,3])2Cu[N(CN)2]Br. We carried out angle-resolved STS on cut lateral surfaces by the focused ion beam (FIB) method as well as as-grown single-crystal surfaces. It was found that the d[3,3]-Br salt is a strong-coupling d-wave superconductor and that the nodal direction is at an angle of π/4 from the a*-axis, corresponding to the dx2-y2 symmetry in the bulk superconducting phase. It is understood that the electron correlation in the d[3,3]-Br salt is not strong enough on the basis of the spin fluctuation mechanism. On the other hand, we also observed two types of superconducting gap. This suggests the coexistence of the dx2-y2 and dxy symmetries. This indicates a change in the symmetry from dx2-y2 in the bulk superconducting phase to dxy around the insulating region with increasing electron correlation. [ABSTRACT FROM AUTHOR]

Electrical resistivity measurements under pressure were conducted on the organic conductor λ-(BEDT-STF)2GaCl4, which is situated between λ-(ET)2GaCl4 and λ-(BETS)2GaCl4. Magnetic susceptibility was also measured at ambient pressure. A drop in resistivity, which is associated with the superconducting transition, was observed at Tc5K above 1.22 GPa. The superconducting phase was confirmed by pair-breaking under a magnetic field. This is the first observation of superconductivity in λ-(BEDT-STF)2GaCl4. The temperature dependence of spin susceptibility suggests a two-dimensional antiferromagnetic spin system without any magnetic ordering. The phase adjacent to the superconducting phase in λ-type systems is not the antiferromagnetic phase, unlike the case for κ-(ET)2X. [ABSTRACT FROM AUTHOR]