Quantum Oscillations in the Topological Superconductor Candidate Cu0.25Bi2Se3

In Cu0.25Bi2Se3, the prime candidate of topological superconductors, quantum oscillations are still not observed in magnetotransport measurement. However, using torque magnetometry, quantum oscillations (the de Haas-van Alphen effect) were observed in Cu0.25Bi2Se3. The doping of Cu in Bi2Se3 increases the carrier density and the effective mass without increasing the scattering rate or decreasing the mean free path. In addition, the Fermi velocity remains the same in Cu0.25Bi2Se3 as that in Bi2Se3. Our results imply that the insertion of Cu does not change the band structure and that conduction electrons in Cu doped Bi2Se3 sit in the linear Dirac-like band.