Double Superconducting Dome and Triple Enhancement of Tc in the Kagome Superconductor CsV3Sb

Abstract

CsV3Sb5 is a newly discovered Z2 topological kagome metal showing the coexistence of a charge density wave (CDW)-like order at T* = 94 K and superconductivity (SC) at Tc = 2.5 K at ambient pressure. Here we study the interplay between CDW and SC in CsV3Sb5 via measurements of resistivity and magnetic susceptibility under hydrostatic pressures. We find that the CDW transition decreases with pressure and experience a subtle modification at Pc1  0.6-0.9 GPa before it vanishes completely at Pc2  2 GPa. Correspondingly, Tc(P) displays an unusual M-shaped double dome character with two maxima around Pc1 and Pc2, respectively, leading to a tripled enhancement of Tc to about 8 K at 2 GPa. The obtained temperature-pressure phase diagram resembles those of many 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 Pc1  P  Pc2 as evidenced by the broad superconducting transition and reduced superconducting volume fraction. This work not only demonstrates the potential to raise the Tc of the V-based kagome superconductors, but also offers more insights into the rich physics related to the electronic correlations in this novel family of topological kagome metals.

Superconductivity modulated by structural phase transitions in pressurized vanadium-based kagome metals

“…Increasing pressure to 10 GPa in RbV 3 Sb 5 and 5 GPa in KV 3 Sb 5 [Figs. 4(b) and (e)], the imaginary phonons associated with the CDW disappear, which indicates the hexagonal P 6/mmm structure is stable at these pressures, consistent with the experimentally observed suppression of CDW above p c ( 2 GPa) [28][29][30]34].…”

“…However, powder XRD measurements at room temperature indicate a hexagonal P 6/mmm structure (α-phase) is adopted up to ≈ 40 GPa [51], seemingly different from our findings in RbV 3 Sb 5 and KV 3 Sb 5 . Nonetheless, for pressures associated with the second superconducting dome, Raman scattering detected sharp changes in the zone-center optical phonons [29] and single crystal XRD revealed the formation of interlayer Sb-Sb bonds [38], both already present at room temperature. Therefore, although CsV 3 Sb 5 maintains a hexagonal P 6/mmm structure at room temperature up to 40 GPa, significant structural modulations occur under pressures associated with the second superconducting dome.…”

“…As a clean and powerful tool that can be utilized to tailor materials' atomic distances, and thus crystal and electronic structures, pressure is widely used to tune the properties of materials. The AV 3 Sb 5 kagome metals are highly tunable by pressure or strain [27][28][29][30][31][32][33][34][35][36][37], and display complex evolution of superconductivity with pressure. Under pressure, the CDW is quickly suppressed at p c 2 GPa, forming a superconducting dome with T c maximized at p c [28][29][30]34], consistent with competing CDW and superconductivity.…”

“…The AV 3 Sb 5 kagome metals are highly tunable by pressure or strain [27][28][29][30][31][32][33][34][35][36][37], and display complex evolution of superconductivity with pressure. Under pressure, the CDW is quickly suppressed at p c 2 GPa, forming a superconducting dome with T c maximized at p c [28][29][30]34], consistent with competing CDW and superconductivity. More strikingly, a second superconducting dome is observed at higher pressures in all variants of AV 3 Sb 5 [27,[30][31][32][33][34], with proposed origins including a Liftshitz transition [31], the formation of a three-dimensional structural network via Sb-Sb bonding [38], an interplay with magnetism [39], and a pressure-induced phase with resistive anomalies [30,34].…”

Role of Sb in the superconducting kagome metal CsV$_3$Sb$_5$ revealed by its anisotropic compression

“…The electronic instabilities in AV 3 Sb 5 further show strong sensitivity to the hydrostatic pressure. The superconducting transition temperature T c changes non-monotonically [20][21][22] and reveals a re-entrant behavior [23] that may be indeed expected in the simple kagome metal when positions of its band saddle points are tuned, and the system goes through several exotic electronic phases, including superconducting phases with unconventional pairing [1,2,4,19,24]. First experimental results suggest that pressure-tuned AV 3 Sb 5 compounds could indeed allow an experimental access to the physics of simple kagome metals with variable positions of band saddle points relative to the Fermi level.…”