Negative Magnetoresistance from Berry Curvature and Orbital Magnetic Moment

Longitudinal negative magnetoresistance has attracted tremendous amount of attention since the emergence of three-dimensional topological materials, e.g. Weyl semimetals, due to the effect of chiral anomaly in these systems. In contrast to the extensively studied longitudinal negative magnetoresistance, transverse magnetoresistance in topological systems has been somewhat overlooked. We formulate transverse magnetoresistance for topological systems with non-zero Berry curvature based on semiclassical Boltzmann theory. Model calculation based on gapped two-dimensional valley systems shows explicitly that magnetoresistance is negative in large range of magnetic field, stemming from Berry curvature and orbital magnetic moment.