Commensurate-to-incommensurate transition of charge-density-wave order and a possible quantum critical point in pressurized kagome metal CsV 3 Sb 5

Clarifying the interplay between charge-density waves (CDWs) and superconductivity is important in the kagome metal CsV 3 Sb 5 , and pressure ( P ) can play a crucial role. Here, we present 121/123 Sb nuclear quadrupole resonance (NQR) measurements under hydrostatic pressures up to 2.43 GPa in CsV 3 Sb 5 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 δ ν of 121/123 Sb-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 δ ν 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.