Commensurability oscillations due to pinned and drifting orbits in a two-dimensional lateral surface superlattice

TL;DR

This paper uses simulations to study how two-dimensional periodic potentials affect electron conduction, revealing that increased modulation suppresses certain oscillations due to guiding center drift, challenging previous theories.

Contribution

The study demonstrates that commensurability oscillations are suppressed by increased potential modulation, highlighting the role of guiding center drift in a 2D electron gas with periodic potentials.

Findings

Increased $V_y$ suppresses $ ho_{xx}(B)$ oscillations.

Oscillations are explained by guiding center drift along potential contours.

Behavior differs from previous perturbation theory predictions.

Abstract

We have simulated conduction in a two-dimensional electron gas subject to a weak two-dimensional periodic potential, $V_x \cos(2\pi x/a) + V_y \cos(2\pi y/a)$. The usual commensurability oscillations in $\rho_{xx}(B)$ are seen with $V_x$ alone. An increase of $V_y$ suppresses these oscillations, rather than introducing the additional oscillations in $\rho_{yy}(B)$ expected from previous perturbation theories. We show that this behavior arises from drift of the guiding center of cyclotron motion along contours of an effective potential. Periodic modulation in the magnetic field can be treated in the same way.