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arXiv · 2303.01225

Commensurate-to-incommensurate transition of charge-density-wave order and a possible quantum critical point in pressurized kagome metal CsV$_3$Sb$_5$

X. Y. Feng·Z. Zhao·J. Luo·J. Yang·A. F. Fang·H. T. Yang·H. J. Gao·R. Zhou·Guo-qing Zheng
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Abstract

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 $\delta\nu$ of $^{121/123}$Sb-NQR spectra increases with cooling down to $T_{\rm CDW}$, indicating the appearance of a short-range CDW order due to CDW fluctuations pinned by quenched disorders. The $\delta\nu$ shows a Curie-Weiss temperature dependence and tends to diverge at $P_{\rm c} \sim$ 1.9 GPa, suggesting that a CDW quantum critical point (QCP) exists at $P_{\rm c}$ where $T_{\rm c}$ shows the maximum. For $P > P_{\rm c}$, spin fluctuations are enhanced when the CDW is suppressed. Our results suggest that the maximal $T_{\rm c}$ at $P_{\rm c} \sim$ 1.9 GPa is related to the CDW QCP and the presence of spin fluctuations prevent the $T_{\rm c}$ from a rapid decrease otherwise after the CDW is completely suppressed.

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X. Y. Feng, Z. Zhao, J. Luo, J. Yang, A. F. Fang, H. T. Yang, H. J. Gao, R. Zhou, Guo-qing Zheng. 2023-03-02. Commensurate-to-incommensurate transition of charge-density-wave order and a possible quantum critical point in pressurized kagome metal CsV$_3$Sb$_5$. https://doi.org/10.1038/s41535-023-00555-w

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