Multigap superconductivity with broken time reversal symmetry in locally noncentrosymmetric SrPtAs

The recently discovered compound SrPtAs has awakened grown scientific interest, because it comprises an exceptional structural feature: it consists of non-centrosymmetric PtAs layers that are weakly coupled to each other. Thus, SrPtAs is a prime example for staggered noncentrosymmetricity. Theoretical calculations predict an unconventional chiral d-wave superconducting state which is unique in material science, but no general consent has been achieved. The evidence for time reversal symmetry breaking was found in μSR experiments, which implies an unconventional superconducting state. Nuclear quadrupole resonance reveals multigap behavior and a fully gapped superconducting state. In particular, I present spin-lattice relaxation rate (1/T₁) measurements and discuss possible pairing symmetries. These results are relevant to understand the pairing mechanism in this and similar compounds. While the fokus is on the experiment, I will discuss the theoretical point of view as well.