  Negative longitudinal magnetoresistance (NLMR) has been reported in a variety
of materials and has attracted extensive attention as an electrotransport
hallmark of topological Weyl semimetals. However, its origin is still under
debate. Here, we demonstrate that the NLMR in a two dimensional electron gas
can be influenced by the measurement current. While the NLMR persists up to 130
K, its magnitude and magnetic field response become dependent on the applied
current below 60 K. The tunable NLMR at low and high currents can be best
attributed to quantum interference and disorder scattering effects,
respectively. This work uncovers non-Ohmic NLMR in a non-Weyl material and
highlights potential effects of the measurement current in elucidating
electrotransport phenomena. We also demonstrate that NLMRs can be a valuable
phenomenon in revealing the origins of other properties, such as negative MRs
in perpendicular magnetic fields.
