Superconducting properties of Rh$_{9}$In$_4$S$_4$ single crystals

TL;DR

This study reports the synthesis and detailed characterization of Rh$_{9}$In$_4$S$_4$ single crystals, revealing bulk superconductivity with a critical temperature around 2.25 K and notable deviations from conventional BCS behavior.

Contribution

The paper presents the first comprehensive investigation of the superconducting properties of Rh$_{9}$In$_4$S$_4$, including thermodynamic, transport, and crystallographic data, highlighting its strong-coupling superconductivity and unusual peak effect.

Findings

Bulk superconductivity with $T_c \\sim$ 2.25 K

Specific heat jump larger than BCS weak coupling value

Observation of a peak effect in resistivity measurements

Abstract

The synthesis and crystallographic, thermodynamic and transport properties of single crystalline Rh$_{9}$In$_4$S$_4$ were studied. The resistivity, magnetization and specific heat measurements all clearly indicate bulk superconductivity with a critical temperature, $T_{c}\sim$ 2.25 K. The Sommerfeld coefficient $\gamma$ and the Debye temperature($\varTheta_{\textrm{D}}$) were found to be 34 mJ mol$^{-1}$ K$^{-2}$ and 217 K respectively. The observed specific heat jump, $\Delta C/\gamma T_{c}$ = 1.66, is larger than the expected BCS weak coupling value of 1.43. Ginzburg-Landau (GL) ratio of the low temperature GL-penetration depth, $\lambda_\text{GL}$$\approx$ 5750\AA, to the GL-coherence length, $\xi_\text{GL}$$\approx$ 94\AA, is large: $\kappa$ $\sim$ 60. Furthermore, we observed a peak effect in the resistivity measurement as a function of both temperature and magnetic field.