Evidence of the nontrivial Berry phase at γ -Al2O3/SrTiO3 heterointerfaces

The nontrivial Berry phase in correlated oxide heterostructures has been highly attractive due to the Rashba spin–orbit interactions originating from the inversion symmetry breaking at the heterointerfaces. Despite the theoretically predicated nontrivial π Berry phase in Rashba systems, its experimental detection among all Rashba oxide interfaces remains elusive. Here, we report a nontrivial Berry phase at the interface between γ-Al2O3 and SrTiO3 as evidenced by the quantum oscillations. Analysis of transport properties under the high magnetic field up to 32 T reveals the weak anti-localization (WAL) effect and Shubnikov–de Haas (SdH) oscillations. Both the WAL effect and the nontrivial π Berry phase extracted from the SdH oscillations manifest the significance of the Rashba spin–orbit coupling in γ-Al2O3/SrTiO3. Physical quantities concerning the Fermi surface, such as effective mass, scattering time, etc., are experimentally accessed as well. Our work provides insights into the nontrivial Berry phase in correlated oxide interfaces.