Unusual competition of superconductivity and charge-density-wave state in a compressed topological kagome metal

Abstract

Understanding the competition between superconductivity and other ordered states (such as antiferromagnetic or charge-density-wave (CDW) state) is a central issue in condensed matter physics. The recently discovered layered kagome metal AV3Sb5 (A = K, Rb, and Cs) provides us a new playground to study the interplay of superconductivity and CDW state by involving nontrivial topology of band structures. Here, we conduct high-pressure electrical transport and magnetic susceptibility measurements to study CsV3Sb5 with the highest Tc of 2.7 K in AV3Sb5 family. While the CDW transition is monotonically suppressed by pressure, superconductivity is enhanced with increasing pressure up to P1 ≈ 0.7 GPa, then an unexpected suppression on superconductivity happens until pressure around 1.1 GPa, after that, Tc is enhanced with increasing pressure again. The CDW is completely suppressed at a critical pressure P2 ≈ 2 GPa together with a maximum Tc of about 8 K. In contrast to a common dome-like behavior, the pressure-dependent Tc shows an unexpected double-peak behavior. The unusual suppression of Tc at P1 is concomitant with the rapidly damping of quantum oscillations, sudden enhancement of the residual resistivity and rapid decrease of magnetoresistance. Our discoveries indicate an unusual competition between superconductivity and CDW state in pressurized kagome lattice.

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].…”

“…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.…”

“…Previous transport measurements on this compound identified the onset of CDW at T CDW = 94 K at ambient pressure [25]. The transition temperature decreases upon compression until the CDW phase disappears around 2 GPa [20], whereas superconducting T c concomitantly increases from 2.5 K to 8 K [21][22][23]. On further compression, T c decreases up to pressures of about 10 GPa and then increases again, thus giving rise to a double-dome structure in the phase diagram and the apparent re-entrant behavior [23,26] that hitherto lacks any microscopic explanation.…”