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arXiv · 2308.15064

Broken time-reversal symmetry in cubic skutterudite-like superconductor Y$_3$Ru$_4$Ge$_{13}$

A. Kataria·J. A. T. Verezhak·O. Prakash·R. K. Kushwaha·A. Thamizhavel·S. Ramakrishnan·M. S. Scheurer·A. D. Hillier·R. P. Singh
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Abstract

The microscopic properties of superconducting cubic skutterudite-like material Y$_3$Ru$_4$Ge$_{13}$ are investigated using muon spin relaxation and rotation ($\mu$SR) measurements. Zero-field $\mu$SR measurements reveal the presence of a spontaneous internal field with a magnitude of $\approx$ 0.18~mT below the superconducting transition temperature, indicating broken time-reversal symmetry in the ground state. In line with previous experiments, transverse-field $\mu$SR measurements are consistent with a fully developed superconductivity gap in Y$_3$Ru$_4$Ge$_{13}$. Our observations point towards the relevance of electronic correlations beyond electron-phonon coupling as origin and indicate that spin-orbit coupling is likely not the key driving force behind the spontaneous breaking of time-reversal symmetry in this system.

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A. Kataria, J. A. T. Verezhak, O. Prakash, R. K. Kushwaha, A. Thamizhavel, S. Ramakrishnan, M. S. Scheurer, A. D. Hillier, R. P. Singh. 2023-08-29. Broken time-reversal symmetry in cubic skutterudite-like superconductor Y$_3$Ru$_4$Ge$_{13}$. https://doi.org/10.1103/physrevb.108.214512

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