Abstract
We report the magnetic and superconducting properties of locally noncentrosymmetric SrPtAs obtained by muon-spin-rotation/relaxation (SR) measurements. Zero-field SR reveals the occurrence of small spontaneous static magnetic fields with the onset of superconductivity. This finding suggests that the superconducting state of SrPtAs breaks time-reversal symmetry. The superfluid density as determined by transverse field SR is nearly flat approaching K proving the absence of extended nodes in the gap function. By symmetry, several superconducting states supporting time-reversal-symmetry breaking in SrPtAs are allowed. Out of these, a dominantly (chiral -wave) order parameter is most consistent with our experimental data.
- Received 14 December 2012
DOI:https://doi.org/10.1103/PhysRevB.87.180503
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