Commensurate-to-incommensurate transition of charge-density-wave order and a possible quantum critical point in pressurized kagome metal CsV3Sb5.

Clarifying the interplay between charge-density waves (CDWs) and superconductivity is important in the kagome metal CsV₃Sb₅, and pressure (P) can play a crucial role. Here, we present ^121/123Sb nuclear quadrupole resonance (NQR) measurements under hydrostatic pressures up to 2.43 GPa in CsV₃Sb₅ single crystals. We demonstrate that the CDW gradually changes from a commensurate modulation with a star-of-David (SoD) pattern to an incommensurate one with a superimposed SoD and Tri-hexagonal (TrH) pattern stacking along the c-axis. Moreover, the linewidth δν of ^121/123Sb-NQR spectra increases with cooling down to T_CDW, indicating the appearance of a short-range CDW order due to CDW fluctuations pinned by quenched disorders. The δν shows a Curie–Weiss temperature dependence and tends to diverge at P_c ~ 1.9 GPa, suggesting that a CDW quantum critical point (QCP) exists at P_c where T_c shows the maximum. For P > P_c, spin fluctuations are enhanced when the CDW is suppressed. Our results suggest that the maximal T_c at P_c ~ 1.9 GPa is related to the CDW QCP, and the presence of spin fluctuations prevents the T_c from a rapid decrease otherwise, after the CDW is completely suppressed. [ABSTRACT FROM AUTHOR]