Simple mechanisms for magnetooscillations NOT to detect Berry phase

Phase of quantum magnetooscilalions is often associated with the Berry phase and is widely used to argue in favor of topological non-triviality of the system (Berry phase $2\pi n+\pi$). Nevertheless, the experimentally determined value may deviate from $2\pi n+\pi$ arbitrarily. In this paper we suggest two simple mechanisms drammatically affecting the experimentally observed value of the phase in three-dimensional topological insulators: (i) magnetic field dependence of the chemical potential, and (ii) possible non-uniformity of the system. These mechanisms are not limited to topological insulators and can be extended to other topologically trivial and non-trivial systems.