Hydrodynamic inverse Faraday effect in a two-dimensional electron liquid

We show that a small conducting object, such as a nanosphere or a nanoring, embedded into or placed in the vicinity of a two-dimensional electron liquid (2DEL) and subjected to a circularly polarized electromagnetic radiation induces “twisted” plasmonic oscillations in the adjacent 2DEL. The oscillations are rectified due to the hydrodynamic nonlinearities leading to the helicity sensitive circular DC current and to a magnetic moment. This hydrodynamic inverse Faraday effect (HIFE) can be observed at room temperature in different materials. The HIFE is dramatically enhanced in a periodic array of the nanospheres forming a resonant plasmonic coupler. Such a coupler exposed to a circularly polarized wave converts the entire 2DEL into a vortex state. Hence, the twisted plasmonic modes support resonant plasmonic-enhanced gate-tunable optical magnetization. Due to the interference of the plasmonic and Drude contributions, the resonances have an asymmetric Fano-like shape. These resonances present a signature of the 2DEL properties not affected by contacts and interconnects and, therefore, providing the most accurate information about the 2DEL properties. In particular, the widths of the resonances encode direct information about the momentum relaxation time and viscosity of the 2DEL.

Figure 1

Excitation of twisted plasmons in 2D electron liquid by a single nanosphere embedded into dielectric matrix and excited by circularly polarized radiation (a) or by an array of nanospheres forming a plasmonic coupler (b).

Figure 2

Different scales of the problem. We predict sharp plasmonic resonances for ${\lambda }_0<d<\sqrt{{\lambda }_0/Q}.$

Figure 3

Dependence of the circular current density, $j_{\mathrm{DC}},$ created in 2D liquid by a rotating dipole moment of a single nanosphere. Main contribution to this current comes from mixed term [see Eq. (28)] .

Figure 4

Frequency dependence of $x-$ component of the current density for $x=y=d/8,R=a/2,d=5a$: onset of plasmonic resonances at large $\gamma$; (a) strongly asymmetric resonances at intermediate values of $\gamma$, (b) weakly asymmetric resonances at very small $\gamma$ (c).

Figure 5

Fundamental plasmonic peak in $x$ component of DC current for $x=y=d/8,R=a/2,d=5a$ and different values of $\gamma .$ The asymmetry of the peak decreases with decreasing of $\gamma .$

Figure 6

Vector density plot of the rectified current density ${\mathbf{j}}_{\text{DC}}$ for different values of parameter $\alpha =2\mathrm{\Omega }{\mu }_0/{\pi }_0$ (here, $x$ and $y$ are measured in units of $d$).

Figure 7

Density plot of $H_z(\mathbf{r},0)$ for different values of parameter $\alpha =2\mathrm{\Omega }{\mu }_0/{\pi }_0$ (here, $x$ and $y$ are measured in units of $d$).

Figure 8

Current-frequency dependence for parameters of InGaAs-based structure with $d=5a=10R=250$ nm at $x=y=d/8$, for two temperatures, 300 and 77 K.