Tuning charge density wave order and superconductivity in the kagome metals KV3Sb5−xSnx and RbV3Sb5−xSnx

Abstract

The family of $A{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$ ($A$ = K, Rb, Cs) kagome metals exhibits charge density wave (CDW) order, proposed to be chiral, followed by a lower temperature superconducting state. Recent studies have proposed the importance of band structure saddle points proximal to the Fermi energy in governing these two transitions. Here we show the effects of hole doping achieved via chemical substitution of Sn for Sb on the CDW and superconducting states in both ${\mathrm{KV}}_{3}{\mathrm{Sb}}_{5}$ and ${\mathrm{RbV}}_{3}{\mathrm{Sb}}_{5}$ and generate a phase diagram. Hole doping lifts the $\mathrm{\ensuremath{\Gamma}}$ pocket and van Hove singularities toward ${E}_{F}$ causing the superconducting ${T}_{C}$ in both systems to increase to about 4.5 K, while rapidly suppressing the CDW state.