Charge puddle-induced linear and nonlinear planar magneto-transport of HgTe-based topological materials

Fluctuations in the planar magnetotransport of topological HgTe structures are observed across both tensile-strained (topological insulator) and compressively strained (Weyl semimetal) phases. We show that these fluctuations stem from the interplay of tilted Dirac cones with the charge puddles, inherently present in the material. The in-plane magnetic field-induced tilt of the Dirac cone emerges if nonlinear momentum terms are included in the dispersion relation. We develop a puddle network model that simulates the transport of tilted Dirac fermions across the potential landscape influenced by charge puddles. The model predicts pronounced magneto-fluctuations comparable with the experimental data. The same charge density puddles also introduce harmonic distortion of the input signal, leading to nonlinearities in the electrical response of the device. These effects extend beyond topological materials; they should occur very generally in narrow-gap systems, wherein the unavoidable presence of charge puddles complicates a clear demonstration of various predicted nonlinear magnetotransport phenomena.