Evidence for an odd-parity nematic phase above the charge-density-wave transition in a kagome metal

Yuji Matsuda

The search for quantum states arising from the interplay between correlation, frustration, and topology is central to condensed matter physics. Recently discovered non-magnetic kagome metals AV₃Sb₅ (A = K, Cs, or Rb) with CDW and superconducting instabilities may host such exotic states. Here we report evidence that an odd-parity electronic nematic state emerges at a higher temperature than the CDW in CsV₃Sb₅ [1]. Our torque measurements reveal a two-fold in-plane magnetic anisotropy that breaks the crystal rotational symmetry. Moreover, in the temperature range between the formation of the CDW and a nematic state, rotating an external magnetic field in a conical fashion yields a distinct first-order phase transition, indicating time-reversal symmetry breaking. These results provide thermodynamic evidence for the emergence of an odd-parity nematic order. In addition, elastoresistance shows no discernible anomalies near the onset of nematicity, consistent with the odd-parity order. These findings suggest that an exotic loop current state precedes the CDW transition in CsV₃Sb₅.

In collaboration with the groups of T. Shibauchi (Univ. Tokyo), H. Kontani (Nagoya Univ.), S. D. Wilson (Univ. of California Santa Barbara), and H. -H. Wen (Nanjing Univ.).

[1] To be published in Nature Phys.