Guiding center linear magnetoresistance in the semi-classical regime

We predict that an unconventional guiding center (GC) motion yields a new mechanism for linear and non-saturating (transverse) magnetoresistance in 3D metals. Our theory is semi-classical and applies in the regime where the transport time is much greater than the cyclotron period, and for weak disorder potentials which are slowly varying on a length scale much greater than the cyclotron radius. Under these conditions, orbits with small momenta along magnetic field B are partially trapped and dominate the transverse conductivity. When disorder potentials are stronger than the Debye frequency, linear magnetoresistance is predicted to survive up to room temperature and beyond. We argue that the new GC magnetoresistance mechanism accounts for the recently observed giant linear magnetoresistance seen in 3D Dirac materials.