  The Berry phase is an important concept in solids, correlated to the band
topology, axion electrodynamics and potential applications of topological
materials. Here, we investigate the magnetotransport and Berry phase of rare
earth element Gd doped Bi2Se3 (Gd_Bi2Se3) topological insulator at low
temperatures and high magnetic fields. Gd_Bi2Se3 single crystals show
Shubnikov-de Haas (SdH) oscillations with nontrivial Berry phase while Bi2Se3
single crystals show zero Berry phase in SdH oscillations. The temperature
dependent magnetization curves can be well fitted with the Curie-Weiss law in
3-300 K region, indicating no magnetic ordering in Gd_Bi2Se3 crystals.
Moreover, Gd doping has limited influence on the quantum oscillation parameters
(e.g., frequency of oscillations, the area of the Fermi surface, effective
electron mass, Fermi wave vectors etc.), but has an impact on the Hall
mobility, carrier density, and band topology. Our results demonstrate that Gd
doping can tune the Berry phase of topological insulators effectively, which
may pave a way for the future realization of many predicted exotic transport
phenomena of topological origin.
