Time-reversal symmetry breaking in superconducting low-carrier-density quasi-skutterudite Lu3Os4Ge13

Abstract

The complex structure of the Remeika phases, the intriguing quantum states they display, and their low carrier concentrations are a strong motivation to study the nature of their superconducting phases. In this work, the microscopic properties of the superconducting phase of single-crystalline Lu${}_3$Os${}_4$Ge${}_{13}$ are investigated by muon-spin relaxation and rotation ($\mu$SR) measurements. The zero-field $\mu$SR data reveal the presence of spontaneous static or quasi-static magnetic fields in the superconducting state, breaking time-reversal symmetry; the associated internal magnetic field scale is found to be exceptionally large ($\approx$ 0.18~mT). Furthermore, transverse-field $\mu$SR measurements in the vortex state of Lu${}_3$Os${}_4$Ge${}_{13}$ imply a complex gap function with significantly different strengths on different parts of the Fermi surface. While our measurements do not completely determine the order parameter, they strongly indicate that electron-electron interactions are essential to stabilizing pairing in the system, thus, demonstrating its unconventional nature.

7 pages, 2 figures

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Cited by in corpus (3)

• Spontaneous time-reversal symmetry breaking by disorder in superconductors
• Broken time-reversal symmetry in cubic skutterudite-like superconductor Y${}_3$Ru${}_4$Ge${}_{13}$
• Anomalous temperature dependence of the electrical resistivity in R${}_3$Co${}_4$Ge${}_{13}$ (R = Y, Lu) single crystals