Superconductivity in TlBi$_2$ with a large Kadowaki-Woods ratio

TL;DR

This study reveals that TlBi$_2$ is a phonon-mediated superconductor with a high electron-phonon coupling, unusual resistivity behavior, and an exceptionally large Kadowaki-Woods ratio, despite weak electron correlations.

Contribution

It is the first detailed investigation of superconductivity and normal state properties of TlBi$_2$, highlighting its large Kadowaki-Woods ratio and strong electron-phonon coupling.

Findings

Bulk superconductivity at 6.2 K in TlBi$_2$

Large electron-phonon coupling constant ($$$_{ep}$ = 1.38)

Unusual T-linear resistivity above 50 K

Abstract

In this article, the superconducting and normal state properties of TlBi$_2$ with the AlB$_2$-type structure were studied by the resistivity, magnetization and specific heat measurements. It was found that bulk superconductivity with $T_{C}$ = 6.2 K emerges in TlBi$_2$, which is a phonon-mediated $s$-wave superconductor with a strong electron-phonon coupling ($\lambda$$_{ep}$ = 1.38) and a large superconducting gap ($\Delta_{0}$/$k_{B}T_{C}$ = 2.25). We found that the $\rho$($T$) exhibits an unusual $T$-linear dependence above 50 K, and can be well described by the Fermi-liquid theory below 20 K. Interestingly, its Kadowaki-Woods ratio $A/\gamma^{2}$ [9.2$\times$10$^{-5}$ $\mu\Omega$ cm(mol K$^{2}$/mJ)$^{2}$] is unexpectedly one order of magnitude larger than that obtained in many heavy Fermi compounds, although the electron correlation is not so strong.