Negative magnetoresistance and sign change of the planar Hall effect due to negative off-diagonal effective mass in Weyl semimetals

We theoretically investigated the magnetoresistance (MR) and planar Hall effect (PHE) in Weyl semimetals based on the semiclassical Boltzmann theory, focusing on the fine structure of the band dispersion. We identified that the negative longitudinal MR and sign change in the PHE occur because of the negative off-diagonal effective mass with no topological effects or chiral anomaly physics. Our results highlight the important role of the off-diagonal effective mass, which can cause anomalous galvanomagnetic effects. We propose that the PHE produces a dip in the temperature dependence, which enables the experimental detection of the singularity of effective mass, i.e., the Weyl point.