There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
Quantum oscillations can be used to determine properties of the Fermi surface of metals
by varying the magnitude and orientation of an external magnetic field. Topological
insulator surface states are an unusual mix of normal and Dirac fermions. Unlike in
graphene and simple metals, Berry's geometric phase in topological insulator surface
states is not necessarily quantised. We show that reliably extracting this geometric
phase from the phase offset associated with the quantum oscillations is subtle. This
is especially so in the presence of a Dirac gap such as that associated with the Zeeman
splitting or interlayer tunneling. We develop a semi-classical theory for general
mixed normal-Dirac systems in the presence of a gap, and in doing so clarify the role
of topology and broken particle-hole symmetry. We propose a systematic procedure of
fitting Landau level index plots at large filling factors to reliably extract the
phase offset associated with Berry's phase.