Super-resonant transport of topological surface states subjected to in-plane magnetic fields

TL;DR

This paper uncovers super-resonant regimes causing pronounced conductance oscillations in topological insulator surface states under in-plane magnetic fields, revealing novel transport phenomena without Landau levels or Aharonov-Bohm effects.

Contribution

It introduces the concept of super-resonant regimes leading to perfect electron transmission in topological surface states under magnetic fields, a novel mechanism for conductance oscillations.

Findings

Pronounced conductance oscillations at large barrier potentials without Landau levels.

Positive magnetoconductance due to Fermi surface expansion from Dirac cone tilting.

Sinusoidal conductance dependence on magnetic field direction with phase shift.

Abstract

Magnetic oscillations of Dirac surface states of topological insulators are expected to be associated with the formation of Landau levels or the Aharonov-Bohm effect. We instead study the conductance of Dirac surface states subjected to an in-plane magnetic field in presence of a barrier potential. Strikingly, we find that, in the case of large barrier potentials, the surface states exhibit pronounced oscillations in the conductance when varying the magnetic field, in the \textit{absence} of Landau levels or the Aharonov-Bohm effect. These novel magnetic oscillations are attributed to the emergence of \textit{super-resonant regimes} by tuning the magnetic field, in which almost all propagating electrons cross the barrier with perfect transmission. In the case of small and moderate barrier potentials, we also identify a positive magnetoconductance which is due to the increase of the Fermi surface by tilting the surface Dirac cone. Moreover, we show that for weak magnetic fields, the conductance displays a shifted sinusoidal dependence on the field direction with period $\pi$ and phase shift determined by the tilting direction with respect to the field direction. Our predictions can be applied to many topological insulators, such as HgTe and Bi$_{2}$Se$_{3}$, and provide important insights into exploring and understanding exotic magnetotransport properties of topological surface states.