Evolution of superconductivity and charge order in pressurized RbV$_3$Sb$_5$

Abstract

The kagome metals AV3Sb5 (A = K, Rb, Cs) under ambient pressure exhibit an unusual charge order, from which superconductivity emerges. In this work, by applying hydrostatic pressure using a liquid pressure medium and carrying out electrical resistance measurements for RbV3Sb5, we find the charge order becomes suppressed under a modest pressure pc (1.4 < pc < 1.6 GPa), while the superconducting transition temperature Tc is maximized. Tc is then gradually weakened with further increase of pressure, before exhibiting another maxima around 22.8 GPa, signifying the presence of a second superconducting dome. Distinct normal state resistance anomalies are found to be associated with the second superconducting dome, similar to KV3Sb5. Our findings point to qualitatively similar temperature-pressure phase diagrams in KV3Sb5 and RbV3Sb5, suggesting a link between the second superconducting dome and the high-pressure resistance anomalies in the AV3Sb5 series. I. INTRODUCTIONThe kagome metals AV 3 Sb 5 (A = K, Rb, Cs) [1-4] have drawn significant interest recently, with focus on (1) superconductivity with topological surfaces states [2], which raises the prospects of realizing topological superconductivity and Majorana zero modes [5,6]; (2) a large anomalous Hall effect in the absence of local moments [7-9], which possibly results from a charge order that breaks time-reversal symmetry [10,11]; (3) nature of the superconducting pairing, with evidence for nodeless superconducting gaps [12-14], as well as indications for nematic superconductivity [15]; and (4) sensitivity of superconductivity and charge order to pressure-tuning [16][17][18][19][20][21][22][23], likely related to the presence of competing instabilities on the kagome lattice [24][25][26][27][28].With the application of pressure, the charge order becomes quickly suppressed and superconductivity is enhanced, forming a superconducting dome with maximal T c near the pressure at which charge order disappears [16][17][18][19][20][21][22]. While this superconducting dome can be understood to result from the competition between superconductivity and charge order, a second superconducting dome is found in AV 3 Sb 5 at higher pressures [16,[19][20][21][22], whose origin remains unclear. Factors that may be relevant for formation of the second superconducting dome include a pressure-induced Lifshitz transition [20], magnetism suppressing superconductivity in the region between the two superconducting domes [29], reconstruction of the Sb bands due to the formation of interlayer Sb-Sb bonds [30], and a distinct highpressure phase revealed through resistivity anomalies [19]. While two-dome superconductivity is found in all AV 3 Sb 5 materials via resistivity measurements [22], studies of the corresponding normal state from which superconductivity emerges has been limited [19,20]. In particular, it remains unclear whether resistivity anomalies associated with a high-pressure phase in KV 3 Sb 5 [19] is also present in RbV 3 Sb 5 and CsV 3 Sb 5 .In addition, single crystal diffra...

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

“…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]. Similar two-dome superconductivity under pressure have been detected in unconventional superconductors, with their origins revealing integral aspects of the physics in these materials.…”

“…To investigate how the crystal structure evolves under pressure and its relation to superconductivity, we carried out systematic powder XRD measurements under pressure. To facilitate a direct comparison with phase diagrams determined using resistivity [30,34], the same liquid pressure medium (silicon oil) is used in the XRD measurements.…”

“…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].…”

Chiral excitonic order from twofold van Hove singularities in kagome metals

“…The application of c-axis pressure suppresses T * and increases T c [37][38][39][40][41][42][43][44]. Applied pressure should change the relative value of the intra/interflavour couplings by changing the separation of the two-dimensional layers, and also shifts the effective values of µ and δ [81].…”