Multi-orbits observed in superconducting Nb-doped Bi$_{2}$Se$_{3}$

Recently discovered superconducting niobium doped Bi$_{2}$Se$_{3}$ shows promise to realize new physical phenomenon including the coexistence of superconductivity and magnetic ordering and possibly topological superconductivity. To understand the new physics showcased in this system, a detailed knowledge of the electronic structure is needed. We present the first observation of quantum oscillations in the magnetization (the de Haas-van Alphen effect) of Nb-doped Bi$_{2}$Se$_{3}$. In the fully superconducting crystal, two distinct orbits are observed, in sharp contrast to Bi$_{2}$Se$_{3}$, Cu-doped Bi$_{2}$Se$_{3}$, and Sr-doped Bi$_{2}$Se$_{3}$. The multiple frequencies observed in our quantum oscillations, combined with our electrical transport studies, indicate the multi-orbit nature of the electronic state of Nb-doped Bi$_{2}$Se$_{3}$.