Evidence for the coexistence of time-reversal symmetry breaking and Bardeen-Cooper-Schrieffer-like superconductivity in La${}_7$Pd${}_3$

Abstract

Time-reversal symmetry breaking (TRSB) with a Bardeen-Cooper-Schrieffer (BCS) -like superconductivity occurs in a small, but growing number of noncentrosymmetric (NCS) materials, although the mechanism is poorly understood. We present heat capacity, magnetization, resistivity, and muon spin resonance/relaxation ($\mu$SR) measurements on polycrystalline samples of NCS La${}_7$Pd${}_3$. Transverse-field $\mu$SR and heat capacity data show La${}_7$Pd${}_3$ is a type-II superconductor with a BCS-like gap structure, while zero-field $\mu$SR results provide evidence of TRSB. We discuss the implications of these results for both the La${}_7{X}_3$ (where $X=$ Ni, Pd, Rh, Ir) group of superconductors and other CS and NCS superconductors for which TRSB has been observed.

12 pages, 7 figures and 2 tables. Accepted in Physical Review B

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• Nodeless superconductivity in the centro- and noncentrosymmetric rhenium-boron superconductors
• Time reversal symmetry breaking and s-wave superconductivity in CaPd2Ge2: A $\mu$SR study
• Quantum muon diffusion and the preservation of time-reversal symmetry in the superconducting state of type-I rhenium
• Time-reversal symmetry breaking in superconducting low-carrier-density quasi-skutterudite Lu3Os4Ge13
• Nodeless time-reversal symmetry breaking in the centrosymmetric superconductor Sc${}_5$Co${}_4$Si${}_{10}$ probed by muon-spin spectroscopy
• Anisotropic superconductivity and unusually robust electronic critical field in single crystal La${}_7$Ir${}_3$
• Pressure induced superconducting dome in LaNiGa2
• NbReSi: A Noncentrosymetric Superconductor with Large Upper Critical Field