Multiband superconducting state and Lifshitz transition in V0.7Re0.3Se2 at high pressure

Tracking the mechanism behind the unconventional superconductors has been recognized as a great challenge and remains one of the major problems in multifields. Layered transition metal dichalcogenides (TMDs) offer an important platform for exploring novel physics. Here, we have discovered that the synergetic Re doping and pressure effect on $\mathrm{V}{\mathrm{Se}}₂$ prompts the appearance of multiband superconductivity at 11.5 GPa with ${T}_{\mathrm{c}}\ensuremath{\sim}3.8\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. By the application of external magnetic fields, this superconducting state is signified by the unusual temperature-upper critical field relationship and the upper critical field characteristic with an upward curvature in the whole pressure range of $12.4\text{--}72.7\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$. The clear experimental evidence of a dominant carrier-type change from electron to hole strongly supports the Lifshitz transition at 37.3 GPa. The tendency of ${T}_{\mathrm{c}}(P)$ with a dome shape derives from the structural transition and Lifshitz transition at 20.9 and 37.3 GPa, respectively. The first-principles calculations further clarify that the $\mathrm{V}\text{\ensuremath{-}}3d, \mathrm{Re}\text{\ensuremath{-}}5d$, and $\mathrm{Se}\text{\ensuremath{-}}4p$ orbitals at the Fermi level contribute to the transformation from the single-band into multiband superconductivity. This work reports the multiband superconductivity in TMDs materials via pressure treatment.