arXiv subjects

Fuyuki Nabeshima

Publications and source records attributed to Fuyuki Nabeshima.

22 records · Page 2Linked to original sources

arXiv2013

Enhancement of the Superconducting Transition Temperature in FeSe Epitaxial Thin Films by Anisotropic Compression

In order to investigate the effects of in-plane strain on the superconductivity of FeSe, epitaxial thin films of FeSe were fabricated on CaF$_2$ substrates. The films are compressed along the a-axis and their superconducting transition temperatures $T_{\mathrm c}^{\mathrm {zero}}$ reach 11.4 K, which is approximately 1.5 times higher than that of bulk crystals. The $T_{\mathrm c}$ values are weakly dependent on the ratio of the lattice constants, $c$ / $a$, compared to that of Fe(Se,Te). Our results indicate that even a binary system FeSe has room for improvement, and will open a new route for the application of Fe-based superconductors.

cond-mat.supr-con↗

arXiv2012

Superconductivity at 5.4 K in $β$-Bi$_2$Pd

We investigate bulk superconductivity in a high-quality single crystal of Bi$_2$Pd ($β$-Bi$_2$Pd, space group; I4/mmm) at temperatures less than 5.4 K by exploring its electrical resistivity, magnetic susceptibility, and specific heat. The temperature dependence of the electrical resistivity shows convex-upward behaviors at temperatures greater than 40-50 K, which can be explained by a parallel-resistor model. In addition, we demonstrate that this material is a multiple-band/multiple-gap superconductor based on the temperature dependences of the specific heat and the upper critical field.

cond-mat.supr-con↗

arXiv2012

Ultralow-dissipative conductivity by Dirac fermions in BaFe$_2$As$_2$

We report on the anomalous behavior of the complex conductivity of BaFe$_{2}$As$_{2}$, which is related to the Dirac cone, in the terahertz (THz)-frequency region. Above the spin-density-wave (SDW) transition temperature, the conductivity spectra follow the Drude model. In the SDW state, the imaginary part of the complex conductivity, $σ_2$, is suppressed in comparison to that expected according to the Drude model. The real part, $σ_1$, exhibits nearly Drude-like behavior. This behavior (i.e., almost no changes in $σ_1$ and the depression of $σ_2$) can be regarded as the addition of extra conductivity without any dissipations in the Drude-type conductivity. The origin of this ultralow-dissipative conductivity is found to be due to conductivity contribution from quasiparticles within the Dirac cone. In other words, we are able to observe the dynamics of Dirac fermions through the conductivity spectra of BaFe$_2$As$_2$, clearly and directly.

cond-mat.supr-con↗

arXiv2011

Effect of Co Impurities on Superconductivity of FeSe0.4Te0.6 single crystals

The effect of Co doping on supercoductivity of FeSe$_{0.4}$Te$_{0.6}$ single crystals is investigated. The superconducting transition temperature decreases linearly for Co doping with the rate -0.75 K/(Co %). On the other hand, the residual resistivity increase is less than 50 $/mu/Omega$cm for 4 % Co doping. These data are consistent with the sign changing interband scattering mechanism of superconductivity ($s_/pm$ symmetry).

cond-mat.supr-con↗