${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ is a newly discovered $Z_2$ topological kagome metal showing the coexistence of a charge-density-wave (CDW)-like order at $T^{*}=94\mathrm{K}$ and superconductivity (SC) at $T_c=2.5\mathrm{K}$ at ambient pressure. Here, we study the interplay between CDW and SC in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ via measurements of resistivity, dc and ac magnetic susceptibility under various pressures up to 6.6 GPa. We find that the CDW transition decreases with pressure and experience a subtle modification at $P_{c1}\approx 0.6–0.9\mathrm{GPa}$ before it vanishes completely at $P_{c2}\approx 2\mathrm{GPa}$. Correspondingly, $T_c(P)$ displays an unusual $M$-shaped double dome with two maxima around $P_{c1}$ and $P_{c2}$, respectively, leading to a tripled enhancement of $T_c$ to about 8 K at 2 GPa. The obtained temperature-pressure phase diagram resembles those of unconventional superconductors, illustrating an intimated competition between CDW-like order and SC. The competition is found to be particularly strong for the intermediate pressure range $P_{c1}\le P\le P_{c2}$ as evidenced by the broad superconducting transition and reduced superconducting volume fraction. The modification of CDW order around $P_{c1}$ has been discussed based on the band structure calculations. This work not only demonstrates the potential to raise $T_c$ of the V-based kagome superconductors, but also offers more insights into the rich physics related to the electron correlations in this novel family of topological kagome metals.

• Received 28 February 2021
• Accepted 18 May 2021

DOI:https://doi.org/10.1103/PhysRevLett.126.247001