Utility of Zeeman-perturbed Nuclear Quadrupolar Resonance in Probing Time Reversal Symmetry Breaking: A Case Study on CDW Sn-doped CsV₃Sb₅

Evidence of time reversal symmetry breaking (TRSB) has been reported in a number of superconducting [1] and charge-density-wave (CDW) systems such as AV₃Sb₅ (A = K, Rb, Cs) [2], with implications for the nature of the order parameter, including the possibility of topological states. However, apparently contradictory experimental results [2, 3] call for an expansion of the suite of experimental probes that are sensitive to TRSB. Here, we examine the utility of Zeeman-perturbed nuclear quadrupolar resonance (ZPNQR) as a probe of orbital magnetism, specifically for application to the AV₃Sb₅ system. The sensitivity of the spin-echo decay to a small magnetic field is studied using a combination of simulations and experiments, for which we document sensitivity improvements by utilizing a variable external magnetic field. For example, a precision of δB < 0.1 G is achieved for 63Cu ZPNQR in Cu₂O in an applied field of 2.0 G. Ongoing work is focused on investigating the influence of strain on the TRSB behavior in CsV₃Sb_5-xSn_x.

1. Ghosh et al., J. Phys.: Condens. Matter 33, 033001 (2021).

2. Xing et al., Nature 631, 60–66 (2024).

3. Saykin et al., Phys. Rev. Lett. 131, 016901 (2023).