  Nonlinear charge transport, including nonreciprocal longitudinal resistance
and nonlinear Hall effect, has garnered significant attention due to its
ability to explore inherent symmetries and topological properties of novel
materials. An exciting recent progress along this direction is the discovery of
significant nonreciprocal longitudinal resistance and nonlinear Hall effect in
the intrinsic magnetic topological insulator MnBi2Te4 induced by the quantum
metric dipole. Given the importance of this finding, the inconsistent response
with charge density, and conflicting requirement of C3z symmetry, it is
imperative to elucidate every detail that may impact the nonlinear transport
measurement. In this study, we reveal an intriguing experimental factor that
inevitably gives rise to sizable nonlinear transport signal in MnBi2Te4. We
demonstrate that this effect stems from the gate voltage oscillation caused by
the application of a large alternating current to the sample. Furthermore, we
propose a methodology to significantly suppress this effect by individually
grounding the voltage electrodes during the second-harmonic measurements. Our
investigation emphasizes the critical importance of thoroughly assessing the
impact of gate voltage oscillation before determining the intrinsic nature of
nonlinear transport in all 2D material devices with an electrically connected
operative gate electrode.
