Photovoltaic effect generated by spin-orbit interactions

An AC electric field applied to a junction comprising two spin-orbit coupled weak links connecting a quantum dot to two electronic terminals is proposed to induce a DC current and to generate a voltage drop over the junction if it is a part of an open circuit. This photovoltaic effect requires a junction in which mirror reflection symmetry is broken. Its origin lies in the different ways inelastic processes modify the reflection of electrons from the junction back into the two terminals, which leads to uncompensated DC transport. The effect can be detected by measuring the voltage drop that is built up due to that DC current. This voltage is an even function of the frequency of the AC electric field.

Figure 1

Illustration of the model system. A quantum dot, represented by a localized energy level, is attached by two weak links lying in the $x-y$ plane to two reservoirs, denoted $L$ and $R$. An AC electric field along $\widehat{\mathbf{z}}$, whose amplitude oscillates with frequency $\mathrm{\Omega }$, induces a Rashba spin-orbit interaction in the links.

Figure 2

The particle current $I_{\mathrm{DC}}$, normalized to $I_0^{}=\left(4{\mathrm{\Gamma }}_L^{}{\mathrm{\Gamma }}_R^{}\right)/\left(\mathrm{\Gamma }\pi \hslash \right)$, calculated from Eq. (21) as a function of $k_{\mathrm{so}}^{}{d}_R^{}$ for $k_{\mathrm{so}}^{}{d}_L^{}=1.0, \epsilon -\mu =0.5\mathrm{\Gamma }$; (a) $\mathrm{\Omega }=0.5\mathrm{\Gamma }$, (b) $\mathrm{\Omega }=2.0\mathrm{\Gamma }$. The increasing dash lengths correspond to $\beta \mathrm{\Gamma }=10.0$, 2.0, 1.0, and 0.5.