Depth-dependent study of time-reversal symmetry-breaking in the kagome superconductor AV3Sb5
J. N. Graham, C. Mielke, Debarchan Das, Tommaso Morresi, V. Sazgari, Andreas Suter, Thomas Prokscha, Hanbin Deng, R. Khasanov, Stephen D. Wilson, Andrea Capa Salinas, Maria Mendes Martins, Yigui Zhong, Kozo Okazaki, Zhiwei Wang, M. Zahid Hasan, Mark H. Fischer, Titus Neupert, J. -X. Yin, S. Sanna, H. Luetkens, Z. Salman, Pietro Bonfà, Z. Guguchia
Abstract
The breaking of time-reversal symmetry (TRS) in the normal state of kagome superconductors AV3Sb5 stands out as a significant feature, but its tunability is unexplored. Using low-energy muon spin rotation and local field numerical analysis, we study TRS breaking as a function of depth in single crystals of RbV3Sb5 (with charge order) and Cs(V0.86Ta0.14)3Sb5 (without charge order). In the bulk of RbV3Sb5 (>33 nm from the surface), we observed an increase in the internal magnetic field width in the charge-ordered state. Near the surface (<33 nm), the muon spin relaxation rate is significantly enhanced and this effect commences at temperatures significantly higher than the onset of charge order. In contrast, no similar field width enhancement was detected in Cs(V0.86Ta0.14)3Sb5, either in the bulk or near the surface. These observations indicate a strong connection between charge order and TRS breaking and suggest that TRS breaking can occur prior to long-range charge order. Time-reversal symmetry breaking has been recently observed in the normal state of kagome superconductors AV3Sb5. Here the authors show that this effect is significantly enhanced near the surface of RbV3Sb5 and occurs at temperatures higher than the onset of charge order, indicating its tunability under zero-field conditions.