Linear nonsaturating magnetoresistance in kagome superconductor CsV₃Sb₅ thin flakes

Linear nonsaturating magnetoresistance (LMR) represents a class of anomalous resistivity response to external magnetic field that has been observed in a variety of materials including but not limited to topological semi-metals, high-T _c superconductors and materials with charge density wave (CDW)/spin density wave orders. Here we report the observation of LMR in layered kagome superconductor and CDW material CsV₃Sb₅ thin flakes, as well as the dimensional crossover and temperature (T) crossover of such LMR. Specifically, in ultrathin CsV₃Sb₅ crystals, the magnetoresistance (MR) exhibits a crossover from LMR at low T to quadratic B dependence above the CDW transition temperature; the MR also exhibits a crossover from LMR to sublinear MR for sample thickness at around ∼20 nm at low T. We discuss several possible origins of the LMR and attribute the effect to two-dimensional CDW fluctuations. Our results may provide a new perspective for understanding the interactions between competing orders in kagome superconductors.