Effects of 2.6-GeV U ion irradiation on the superconductivity of the kagome superconductors CsV3Sb5 and Cs

We have investigated the effect of 2.6-GeV U irradiation on the superconductivity of $\mathrm{Cs}{\mathrm{V}}_{3}\mathrm{S}{\mathrm{b}}_{5}$ and $\mathrm{Cs}{({\mathrm{V}}_{0.93}\mathrm{N}{\mathrm{b}}_{0.07})}_{3}\mathrm{S}{\mathrm{b}}_{5}$ single crystals by using resistivity and magnetization measurements. The critical transition temperature for $\mathrm{Cs}{\mathrm{V}}_{3}\mathrm{S}{\mathrm{b}}_{5}$ crystal is enhanced up to 4.3 K after irradiation with a dose of ${B}_{\mathrm{\ensuremath{\Phi}}}=2.0\phantom{\rule{0.28em}{0ex}}\mathrm{T}$, while the critical current density is increased up to $\ensuremath{\sim}0.8\ifmmode\times\else\texttimes\fi{}{10}^{4}\phantom{\rule{0.28em}{0ex}}\mathrm{A}/\mathrm{c}{\mathrm{m}}^{2}$ after irradiation with a dose of ${B}_{\mathrm{\ensuremath{\Phi}}}=0.5\phantom{\rule{0.28em}{0ex}}\mathrm{T}$ under self-field at 2.0 K, which is about four times larger than that for the pristine crystal under the same condition. For $\mathrm{Cs}{({\mathrm{V}}_{0.93}\mathrm{N}{\mathrm{b}}_{0.07})}_{3}\mathrm{S}{\mathrm{b}}_{5}$ crystal, the critical transition temperature remains almost constant up to ${B}_{\mathrm{\ensuremath{\Phi}}}=2.0\phantom{\rule{0.28em}{0ex}}\mathrm{T}$, followed by monotonic suppression with further increase of dose. Besides the enhanced critical current density, we observe an anomalous peak effect in the magnetic hysteresis loop close to zero field at low irradiation doses, which can be interpreted by the matching effect in irradiated $\mathrm{Cs}{({\mathrm{V}}_{0.93}\mathrm{N}{\mathrm{b}}_{0.07})}_{3}\mathrm{S}{\mathrm{b}}_{5}$ crystals.