We show that the observed time-reversal symmetry breaking (TRSB) of the superconducting state in can be understood as originating from inhomogeneous strain fields near edge dislocations of the crystal. Specifically, we argue that, without strain inhomogeneities, is a single-component, time-reversal symmetric superconductor, likely with symmetry. However, due to the strong strain inhomogeneities generated by dislocations, a slowly decaying subleading pairing state contributes to the condensate in significant portions of the sample. As it phase winds around the dislocation, time-reversal symmetry is locally broken. Global phase locking and TRSB occur at a sharp Ising transition that is not accompanied by a change of the single-particle gap and yields a very small heat capacity anomaly. Our model thus explains the puzzling absence of a measurable heat capacity anomaly at the TRSB transition in strained samples and the dilute nature of the time-reversal symmetry broken state probed by muon spin rotation experiments. We propose that plastic deformations of the material may be used to manipulate the onset of broken time-reversal symmetry.
Bibliographical noteFunding Information:
Deutsche Forschungsgemeinschaft U.S. Department of Energy University of Minnesota
We are grateful to Erez Berg, Martin Greven, Clifford Hicks, Steven A. Kivelson, Avraham Klein, You-Sheng Li, Andrew P. Mackenzie, Brad Ramshaw, and Andrew Chang Yuan for fruitful discussions. R.W., M.H., and J.S. were supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - TRR 288-422213477 Elasto-Q-Mat (project B01). R.M.F. was supported by the U.S. Department of Energy through the University of Minnesota Center for Quantum Materials, under Grant No. DE-SC-0016371. R.M.F. also acknowledges a Mercator Fellowship (TRR 288 - 422213477) from the German Research Foundation (DFG).
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