Superconductivity of VSe2 under pressure and charge doping: Suppressed charge density wave

By employing the first -principles calculations, the influence mechanism of external pressure and charge doping on the electron -phonon coupling (EPC) and superconductivity (SC) of bulk VSe 2 is investigated. Our calculations reveal that with increasing pressure the charge density wave (CDW) of 1T-VSe 2 is gradually suppressed, and a SC state subsequently emerges which is accompanied by a structural phase transition from the trigonal phase to a monoclinic phase at 15 . 5 GPa. Increasing pressure from 15.5 to 35 GPa, the SC transition temperature T c of VSe 2 slightly increases from 4.2 to 5 . 2 K and no SC dome is found, which are in good agreement with the previous experimental results [S. Sahoo et al. , Phys. Rev. B 101 , 014514 (2020)]. Through electron- or hole -doping (denoted by n e and n h ), the CDW order of the trigonal phase can be suppressed and SC states with T c greater than 10.5 and 9 . 0 K, respectively, emerge. The highest T c under charge doping can be up to about 12 K, and a weak double -dome like dependence of T c on n e and n h is found. Combining systematical analysis of effects of pressure and charge doping, we demonstrate that the Kohn anomalies of phonons at certain Q points associated with the in -plane vibrations of V atoms play key roles in strengthening the EPC, which brings about the intriguing SC in VSe 2 . However, due to the weak pressure -induced modifications of phonon spectrum as well as Fermi surface (FS), the changes of EPC and T c caused by pressure are not significant. Interestingly, charge doping will produce a local flat band along P A direction near the FS, which is mainly contributed by V 3 d -orbitals, and result in large values of electronic density of states at Fermi level. Therefore, the effects caused by charge doping to the electronic structures, phonon anomalies, EPC, and T c are evident. Our findings may provide a promising understanding to the pressure and doping -dependent SC of VSe 2 , and may be valuable for designing new materials with enhanced SC through the strategic manipulation of electronic and phononic properties.