Uniaxial strain tuning of charge modulation and singularity in a kagome superconductor.

Tunable quantum materials hold great potential for applications. Of special interest are materials in which small lattice strain induces giant electronic responses. The kagome compounds AV₃Sb₅ (A = K, Rb, Cs) provide a testbed for electronic tunable states. In this study, through angle-resolved photoemission spectroscopy, we provide comprehensive spectroscopic measurements of the electronic responses induced by compressive and tensile strains on the charge-density-wave (CDW) and van Hove singularity (VHS) in CsV₃Sb₅. We observe a tripling of the CDW gap magnitudes with ~ 1% strain. Simultaneously, changes of both energy and mass of the VHS are observed. Combined, this reveals an anticorrelation between the unconventional CDW order parameter and the mass of the VHS, and highlight the role of the latter in the superconducting pairing. The substantial electronic responses uncover a rich strain tunability of the versatile kagome system in studying quantum interplays under lattice variations. The authors report that tensile strain applied to CsV₃Sb₅ strongly suppresses the charge-density-wave (CDW) gap, increases the mass of the fermions at the higher-order van Hove singularity (HO-VHS) and drives the energy of the HO-VHS towards the Fermi energy. Further, they suggest an important role of the HO-VHS in superconducting pairing. [ABSTRACT FROM AUTHOR]