Revealing the competition between charge density wave and superconductivity in CsV₃Sb₅ through uniaxial strain

In this talk, I will discuss the effect of uniaxial strain ε applied on the newly discovered Kagome superconductor CsV₃Sb₅ [1]. At ambient conditions, CsV₃Sb₅ shows a charge-density-wave (CDW) transition at T_CDW=94.5K and superconducts below T_c = 3.34 K. We revealed that when the uniaxial strain ε is varied from -0.90% to 0.90%, T_c monotonically increases by ~ 33%. On the other hand, for ε changing from -0.76% to 1.26%, T_CDW decreases monotonically by ~10%. The opposite response of T_c and T_CDW to the uniaxial strain suggests strong competition between these two orders. Comparison with hydrostatic pressure measurements indicates that it is the change in the c-axis that is responsible for these behaviors of the CDW and superconducting transitions, and that the explicit breaking of the sixfold rotational symmetry by strain has a negligible effect. Together with the theoretical studies, we propose that the trilinear coupling between the M+1 and L-2 phonon modes plays an important role in the CDW.

[1] Tiema Qian, et al., PHYSICAL REVIEW B 104, 144506 (2021) Editors' Suggestion