Chiral pumping effect induced by rotating electric fields

We propose an experimental setup using 3D Dirac semimetals to access a novel phenomenon induced by the chiral anomaly. We show that the combination of a magnetic field and a circularly polarized laser induces a finite charge density with an accompanying axial current. This is because the circularly polarized laser breaks time-reversal symmetry and the Dirac point splits into two Weyl points, which results in an axial-vector field. We elucidate the appearance of the axial-vector field with the help of the Floquet theory by deriving an effective Hamiltonian for high-frequency electric fields. This anomalous charge density, i.e., the chiral pumping effect, is a phenomenon reminiscent of the chiral magnetic effect with a chiral chemical potential. We explicitly compute the pumped density and the axial-current expectation value. We also take account of coupling to the chiral magnetic effect to calculate a balanced distribution of charge and chirality in a material that behaves as a chiral battery.

Figure 1

Experimental setup with the magnetic field and the circularly polarized laser onto a 3D Dirac semimetal.

Figure 2

Pseudoenergies $\pm {\varepsilon }_{-}\left(p\right)$ as a function of $p^{x,y}=\sqrt{p_x^2+p_y^2}$ and $p^z$ for $\beta >m$ [in the figure $(m,\beta )=(1,5)$ was chosen].

Figure 3

Energy dispersion relations of the LLL (i.e., $p^x=p^y=0)$ with (a) chiral chemical potential ${\mu }_{\mathrm{A}}$ relevant for the CME and (b) chiral shift $\beta$ relevant for the CPE. Filled (blank) dots represent states that are newly occupied (unoccupied).