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μSR study of time-reversal symmetry constraints and bulk superfluid response in Li0.95FeAs

Rustem Khasanov1,*, Hubertus Luetkens1, and Nikolai D. Zhigadlo2

  • 1PSI Center for Neutron and Muon Sciences CNM, 5232 Villigen PSI, Switzerland
  • 2CrystMat Company, CH-8037 Zurich, Switzerland

  • *Contact author: rustem.khasanov@psi.ch
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Phys. Rev. B 114, 094509 – Published 13 August, 2026

DOI: https://doi.org/10.1103/zlzx-qty2

Abstract

We report zero-field (ZF) and transverse-field (TF) muon-spin rotation/relaxation (μSR) measurements on superconducting Li0.95FeAs (Tc≃16.0K) grown by a high-pressure self-flux method. The ZF-μSR data show no detectable change of the electronic relaxation rate on cooling through Tc, providing no evidence for time-reversal-symmetry breaking in the superconducting state. TF-μSR measurements reveal a well-developed vortex response with strong flux pinning and a negligible nonsuperconducting contribution, confirming that superconductivity is a bulk property of the sample. From the second moment of the internal field distribution we determine a low-temperature in-plane magnetic penetration depth λab=245(15) nm. The temperature dependence of the normalized superfluid density is well described by an effective two-gap model with Δ1=2.0(2)meV and Δ2=0.7(2)meV. A quantitative comparison with band weights derived from angle-resolved photoemission spectroscopy shows that the μSR response is dominated by the Fermi-surface sheets carrying the intermediate and small superconducting gaps, whereas the band hosting the largest gap contributes only about 3% to the total superfluid density and is therefore not resolved in the present analysis. Taken together, these results provide an independent bulk confirmation of nodeless multigap superconductivity in Li0.95FeAs without detectable time-reversal-symmetry breaking and show how μSR reconciles the gap scales reported by bulk- and surface-sensitive probes in this multiband system.

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Phys. Rev. B 114, 094509– Published 13 August, 2026
  • Received 15 April 2026
  • Revised 10 June 2026
  • Accepted 10 July 2026
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