Intertwined charge-density-wave order in vanadium-based kagome superconductors

Abstract

In correlated quantum materials, the intertwinement of multiple orders leads to rich exotic quantum states of matter and emergent phenomena. Recently, the discovery of superconductivity and charge density waves (CDWs) with multiple symmetry breakings in kagome superconductors AV3Sb5 (A = K, Rb, Cs) offers a new territory to study intertwined orders. Elastoresistance, which detects the electric resistance in response to an applied strain, offers a unique method to investigate the evolution of intertwined orders in AV3Sb5. Here, we perform a systematic measurement of elastoresistance in two hole-doped CsV3Sb5 series: CsV3Sb5-ySny (y = 0.04 and 0.06) and CsV3-xTixSb5 (x = 0.03, 0.05 and 0.09). Below the CDW transition temperature (TCDW), the elastoresistance coefficient in all samples undergoes a jump-like transition at TCDW and then another kink-like transition at a lower temperature (T*). Based on a Ginzburg-Landau analysis of CDW order, the jump-like transition at TCDW is well explained by a triple-Q CDW driven by lattice instability, while the kink-like transition around T* is ascribed to an interaction-driven quantum melting of triple-Q CDW, which leads to a nematic CDW state at low temperatures. Interestingly, the T* in all samples follows a perfect anti-correlation with the superconducting transition temperature (Tc), indicating an intertwinement of superconductivity and nematic CDW. Strikingly, the elastoresistance coefficient of Sn-doped samples exhibits a distinct temperature dependence from that of pristine and Ti-doped samples above TCDW, which is ascribed to a charge stripe instability enhanced by Sn doping. Our present findings provide a new perspective to understand the intertwined orders in kagome superconductors AV3Sb5.