Search for time-reversal symmetry breaking in Re-based compound ReAl6

A unique characteristic of the specific complex order parameters in noncentrosymmetric (NCS) superconductors (SCs) is time-reversal symmetry breaking (TRSB). The intermetallic Re6X-NCS SCs are of particular interest since most of the members in this family have been found to exhibit TRSB. Here, TRSB is believed to be due to the local electronic structure of Re. However, the critical questions remain (i) why such energetics that would drive such state occur only in systems with Re and (ii) if TRSB is a universal feature of systems containing Re. We believe that to answer these questions, it is essential to examine other Re-based families of superconductors. In this proposal, we propose to measure a new Re-based centrosymmetric superconductor ReAl6 using muon relaxation/rotation measurements. Here we can directly study the presence/absence of the effects due to Re electronic structure.