Photocurrent Induced by a Bicircular Light Drive in Centrosymmetric Systems

A bicircular light (BCL) consists of left and right circularly polarized lights with different frequencies, and draws a roselike pattern with a rotational symmetry determined by the ratio of the two frequencies. Here we show that an application of a BCL to centrosymmetric systems allows a photocurrent generation through introduction of an effective polarity to the system. We derive formulas for the BCL-induced photocurrent from a standard perturbation theory, which is then applied to a simple 1D model and 3D Dirac and Weyl semimetals. A nonperturbative effect with strong light intensity is also discussed with the Floquet technique.

Figure 1

Schematics of bicircular light (BCL) that consists of circularly polarized light (CPL) with different frequencies. (a) The electric field of the BCL draws the roselike pattern with a rotational symmetry determined by the ratio of the two frequencies. The rose patterns with $n_1=1$, $n_2=n$ in Eq. (1) are plotted. (b) The relative phase between two CPL waves leads to rotation of the rose pattern of the BCL. (c) Application of BCL to centrosymmetric systems can induce a photocurrent with the introduction of an effective polarity.

Figure 2

A BCL-induced photocurrent in the 1D SSH model. (a) A schematic picture of the SSH model driven by threefold BCL. (b) The band dispersion of the SSH model. The minimum (maximum) input frequency ${\mathrm{\Omega }}_{\min }$ (${\mathrm{\Omega }}_{\max }$) is depicted with the green (blue) arrow. (c) Photocurrent dependence on the input frequency (we set $\delta t_0=0.5t_0$).

Figure 3

The BCL-induced photocurrent in Dirac and Weyl semimetals. (a) A schematic picture of a single Dirac cone driven by threefold BCL. Pauli blocking prohibits the photoexcitation with the $\mathrm{\Omega }$ ($2\mathrm{\Omega }$) resonant process for frequencies $\hslash \mathrm{\Omega }<2|{\epsilon }_F|$ ($2\hslash \mathrm{\Omega }<2|{\epsilon }_F|$) with the chemical potential ${\epsilon }_F$. The orange line indicates Pauli blocking for the $\mathrm{\Omega }$-resonant process. (b) Photocurrent dependence on the frequency. We set $\eta =0.8$. The green (blue) arrow represents the frequency range where the $\mathrm{\Omega }$ ($2\mathrm{\Omega }$) resonant process is allowed.

Figure 4

Nonperturbative effect on the BCL-induced photocurrent. (a) The amplitude dependence of the photocurrent with several relaxation rate values ${\gamma }_0$. (b) The amplitude dependence of the photocurrent at ${\gamma }_0/t_0=0.02$ with fitting curves of $J\propto A_0^3$ (red line) and $J\propto A_0^{1.7}$ (blue line). We set $\hslash \mathrm{\Omega }/t_0=1.2$.