Manipulation of time reversal symmetry breaking superconductivity in Sr2RuO4 by uniaxial stress
Although the normal-state electronic structure of Sr2RuO4 is known with exceptional precision, even after two decades of research, the symmetry of its certainly unconventional superconducting state is under strong debate. In general, time-reversal-symmetry breaking (TRSB) superconductivity indicates complex two-component order parameters. Probing Sr2RuO4 under uniaxial stress offers the possibility to lift the degeneracy between such components. One key prediction for Sr2RuO4, a splitting of the superconducting and TRSB transitions under uniaxial stress has not been observed so far. I will show results of muon spin relaxation (μSR) measurements on Sr2RuO4 placed under uniaxial stress, wherein a large stress-induced splitting between the onset temperatures of superconductivity and TRSB was observed . Moreover, at high stress beyond the Van Hove singularity, a new spin density wave ordered phase was detected for the first time. To perform μSR measurements under uniaxial stress, a custom piezoelectric based pressure cell was developed . This cell is going to be useful for a range of other materials, in which the Fermi surface or magnetic interaction strengths can be tuned leading to strong modifications of the electronic state.
 V. Grinenko*, S. Ghosh* et al., Nature Physics 17, 748–754 (2021).
 S. Ghosh et al., Review of Scientific Instruments 91, 103902 (2020).
About the QSQM: The EFRC-QSQM center aims to develop and apply nontrivial quantum sensing to measure and correlate local and nonlocal quantum observables in exotic superconductors, topological crystalline insulators, and strange metals. The center is led by the University of Illinois at Urbana-Champaign in partnership with the University of Illinois at Chicago and the SLAC National Accelerator Laboratory.