Negative longitudinal magnetoconductance at weak fields in Weyl semimetals

Weyl semimetals are topological materials that provide a condensed-matter realization of the chiral anomaly. A positive longitudinal magnetoconductance quadratic in magnetic field has been promoted as a diagnostic for this anomaly. By solving the Boltzmann equation analytically, we show that the magnetoconductance can become negative in the experimentally relevant semiclassical regime of weak magnetic fields. This effect is due to the simultaneous presence of the Berry phase and the orbital magnetic moment of carriers and occurs for sufficiently strong intervalley scattering.

Figure 1

Sketch of the Fermi surface surrounding a Weyl node if the OMM is not (left) or is (right) taken into account. The inclusion of the OMM leads to an egg-shaped Fermi surface, and the magnetoconductance can be either positive or negative, depending on the scattering amplitudes.

Figure 2

Current density $j_z\left(B\right)/j_z\left(0\right)$ as a function of $eB{v}_F^2/2{\mu }^2$ in the presence (orange curves) and absence (blue curves) of the OMM. For the solid curves, the intervalley scattering amplitude is equal to the intravalley scattering amplitude, $V_{\mathrm{intra}}=V_{\mathrm{inter}}=3$, whereas for the dashed curves, $V_{\mathrm{inter}}=1.5$ is half as large as $V_{\mathrm{intra}}=3$.