Enhancement of superconductivity and phase diagram of Ta-doped Kagome superconductor CsV₃Sb₅

Kagome superconductors AV₃Sb₅ (A = K, Rb, and Cs) have attracted enormous interest due to the coexistence of charge density wave (CDW) order, unconventional superconductivity (SC) and anomalous Hall effect (AHE). In this paper, we reported an intensive investigation on Cs(V_1−xTa_x)₃Sb₅ single crystals with systematic Ta doping. Ta was confirmed to be doped into V-site in the Kagome layer from both single crystal X-ray diffraction structural refinement and scanning transmission electron microscopy observation. The highest Ta doping level was found to be about 16%, which is more than twice as much as 7% in Nb-doped CsV₃Sb₅. With the increase of Ta doping, CDW order was gradually suppressed and finally vanished when the doping level reached to more than 8%. Meanwhile, superconductivity was enhanced with a maximum critical temperature (Tc) of 5.3 K, which is the highest Tc in the bulk crystal of this Kagome system at ambient pressure so far. The μ₀H_c2(T) behavior demonstrates that the system is still a two-band superconductor after Ta doping. Based on the electrical transport measurement, a phase diagram was set up to exhibit the evolution of CDW and SC in the Cs(V_1−xTa_x)₃Sb₅ system. These findings pave a new way to search for new superconductors with higher Tc in the AV₃Sb₅ family and establish a new platform for tuning and controlling the multiple orders and superconducting states.