Effect of hydrostatic pressure on the unconventional charge density wave and superconducting properties in two distinct phases of doped kagome superconductors CsV3−xTixSb5

Recent studies on the kagome metal ${\mathrm{CsV}}₃{\mathrm{Sb}}₅$ have revealed an intricate interplay between unconventional charge density waves (CDWs) and superconductivity (SC). Substitutions of Ti for V can perturb the CDW and produce two distinct SC phases with different pairing symmetries in the series of $\mathrm{Cs}{\mathrm{V}}_{3\ensuremath{-}x}{\mathrm{Ti}}_x{\mathrm{Sb}}₅$. Here, we performed a comprehensive high-pressure study on Ti-doped $\mathrm{Cs}{\mathrm{V}}_{3\ensuremath{-}x}{\mathrm{Ti}}_x{\mathrm{Sb}}₅$ ($x=0.04,0.15$) samples to elucidate the combined effects of physical pressure and chemical doping on the coexistence of CDWs and SC. Under high pressures, the M-shaped double superconducting dome observed in the parent ${\mathrm{CsV}}₃{\mathrm{Sb}}₅$ is retained but very weakened for $x=0.04$, and it is replaced by a single broad superconducting dome for $x=0.15$. Accordingly, the optimal superconducting ${T}_{\mathrm{c}}$ under high pressures decreases gradually with increasing Ti-doping level. On the other hand, the upper critical field first exhibits an obvious rise with enhanced flux pinning effects by disorders for $x=0.04$ and then is suppressed upon further increasing Ti doping. The constructed $T\text{\ensuremath{-}}P$ phase diagrams of $\mathrm{Cs}{\mathrm{V}}_{3\ensuremath{-}x}{\mathrm{Ti}}_x{\mathrm{Sb}}₅$ reveal the competition and coexistence of CDWs and SC. Our results provide more insight into the intertwined competing electronic orders in the Ti-doped kagome superconductors $\mathrm{Cs}{\mathrm{V}}_{3\ensuremath{-}x}{\mathrm{Ti}}_x{\mathrm{Sb}}₅$.