Peak Effects in the Kagome Superconductors CsV3Sb5 and Cs(V0.93

The effect of 3 MeV proton irradiation on the superconductivity of ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$ and $\mathrm{Cs}{({\mathrm{V}}_{0.93}{\mathrm{Nb}}_{0.07})}_{3}{\mathrm{Sb}}_{5}$ has been investigated by resistivity and magnetization measurements. The critical transition temperature ${T}_{\mathrm{c}}$ increases from 3.2 to 4.4 K after proton irradiation for ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$ single crystals. Besides the enhanced critical current density, we observe a broad magnetization peak in the proton-irradiated ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$ single crystals, which can be attributed to the enhancement of vortex pinning induced by irradiation. We find the magnetization peak close to the upper critical field ${H}_{\mathrm{c}2}$ in $\mathrm{Cs}{({\mathrm{V}}_{0.93}{\mathrm{Nb}}_{0.07})}_{3}{\mathrm{Sb}}_{5}$ single crystals, which should come from the softening of the flux line lattice. The ${T}_{\mathrm{c}}$ is slightly suppressed after proton irradiation in $\mathrm{Cs}{({\mathrm{V}}_{0.93}{\mathrm{Nb}}_{0.07})}_{3}{\mathrm{Sb}}_{5}$ single crystals at the present irradiation doses. The vortex phase diagrams have been constructed for the kagome superconductors $\mathrm{Cs}{({\mathrm{V}}_{0.93}{\mathrm{Nb}}_{0.07})}_{3}{\mathrm{Sb}}_{5}$ and proton-irradiated ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$ based on the obtained data.