Gate electrode-induced nonreciprocal resistance in topological insulators

A common method of controlling the chemical potential in topological insulators is applying a gate electrode. Simultaneously applying high source-drain bias currents can lead to parasitic effects in such devices. We derive that these parasitic effects lead to a gradient in the Hall effect along the current lead of a Hall bar. Consequently, nonreciprocal effects in both longitudinal and Hall voltages appear upon reversing the bias. These effects scale similarly to the magnetochiral anisotropy, requiring detailed analysis to make a distinction. Experimentally we show that nonreciprocal effects can appear in materials where magnetochiral anisotropy is not expected while a top gate is present. Without gate electrode, this nonreciprocal effect is found to be absent. These results show the importance of considering and, if possible, excluding gate electrode-induced effects when searching for nonreciprocal resistance intrinsic to a material.