Photovoltaic chiral magnetic effect in Weyl semimetals

We theoretically predict current generation in Weyl semimetals when circularly polarized light is applied. The electric field of the light can drive an effective magnetic field on the order of 10 T. For lower-frequency light, a nonequilibrium spin distribution is formed near the Fermi surface. Spin-momentum locking induces a giant electric current proportional to the effective magnetic field. In contrast, higher-frequency light realizes a quasistatic Floquet state with no induced electric current. We discuss the relevant materials and estimate the order of magnitude of the induced current.

Figure 1

Schematic illustration of photovoltaic chiral magnetic effect: (a) For a lower-frequency light regime, electrons near the Fermi surface are excited by incident light through the Raman process illustrated. As a result, a finite spin distribution is generated near the Fermi surface, and the spin of Weyl fermions is aligned in the direction of the effective magnetic field ${\mathit{B}}^{\mathrm{eff}}$, on average. (b) For the reason given above, the circularly polarized light aligns the spin of Weyl fermions. Because of (pseudo)spin-momentum locking, Weyl fermions with helicity $\sigma =1(\sigma =-1)$ move in the same (opposite) direction as the spin, which results in nonzero current ${\mathit{j}}_{\sigma }$.

Figure 2

Diagrammatic representation of a charge current $\langle j_{\sigma }^i\rangle$ via the photovoltaic chiral magnetic effect (a) without and (b–d) with a vertex correction for nonmagnetic impurity scattering. Wavy lines denote the electric field of the polarized light.