Pressure-induced electronic anomaly and multiband superconductivity in the doped topological insulator NbxBi2Se3

The tunability of the electronic topological transition is fundamentally important to unveil new quantum matters. Here, we report the observation of pressure-induced electronic anomaly below 12.0 GPa in Nb0.25Bi2Se3 using a combination of electrical transport, synchrotron x-ray diffraction, Raman-scattering spectroscopy measurements, and first-principles calculations. At ambient pressure, the band-structure calculations demonstrate the Nb0.25Bi2Se3 is a heavily electron-doped semiconductor with multiple band structure. With applying pressure, it is shown that the pressure can induce Fermi-surface reconstruction at a time-reversal invariant point. We further present evidence of multiband superconductivity characterized by an upward curvature in the upper critical field in the pressurized Nb0.25Bi2Se3 crystal. The superconducting critical parameters of pressurized Nb0.25Bi2Se3 crystal are obtained. Furthermore, the superconducting phase diagram under high pressure is discussed within BCS theory. These findings highlight the critical role of the multiple-band structure induced by strong hybridization between the Nb-4d and Bi/Se-p orbitals in accessing quantum states.