Peak effects in the kagome superconductors CsV3Sb5 and Cs(V0.93Nb0.07)3Sb5

The effect of 3 MeV proton irradiation on the superconductivity of CsV3Sb5 and Cs(V0.93Nb0.07)3Sb5 has been investigated by resistivity and magnetization measurements. The critical transition temperature Tc increases from 3.2 to 4.4 K after proton irradiation for CsV3Sb5 single crystals. Besides the enhanced critical current density, we observe a broad magnetization peak in the proton-irradiated CsV3Sb5 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 Hc2 in Cs(V0.93Nb0.07)3Sb5 single crystals, which should come from the softening of the flux line lattice. The Tc is slightly suppressed after proton irradiation in Cs(V0.93Nb0.07)3Sb5 single crystals at the present irradiation doses. The vortex phase diagrams have been constructed for the kagome superconductors Cs(V0.93Nb0.07)3Sb5 and proton-irradiated CsV3Sb5 based on the obtained data.