Magnetic-field-induced nonlinear optical responses in inversion symmetric Dirac semimetals

We show that under the effect of an external magnetic field, a photogalvanic effect and the generation of a second harmonic wave can be induced in inversion symmetric and time-reversal invariant Dirac semimetals and it is linear with the magnetic field. The mechanisms responsible for these nonlinear optical responses are the magnetochiral effect and the chiral magnetic effect. What makes possible that these two effects give rise to the discussed nonlinear optical effects is the presence of band bending effects in the dispersion relation in real Dirac semimetals. Some observable consequences of this phenomenon are the appearance of a dc current on the surface of the system when it is irradiated with linearly polarized light or a rotation of the polarization plane of the reflected second harmonic wave.

Figure 1

Band structure for Dirac semimetals. (a) The two-band model used in the text. The separation between nodes, the band bending, and the curvature in the dispersion relation is apparent. (b) The approximate linear dispersion relation around each Weyl node. The bands corresponding to the two Kramers partners are superimposed.

Figure 2

(a) Prototypical experimental setup employed to measure the surface current generated by linearly polarized light. A second ammeter can be used to simultaneously measure the other component of the current. (b) Angular dependence of the components of the induced current ${\mathit{J}}^{LPGE}$ as a function of the polarization angle $\alpha$ of the incident light.