Synopsis: Current Flow While in Equilibrium

In a superconductor-semiconductor hybrid system, circularly polarized light can generate an electric current without the system leaving thermal equilibrium.
Synopsis figure
A. G. Mal’shukov, Phys. Rev. Lett. (2011)

When circularly polarized light shines on a semiconductor, it creates a population of polarized carriers, which in turn induce a dc electric current, an effect known as the circular photogalvanic effect (CPE). In order for this effect to take place, the light beam must be able to create a nonequilibrium distribution of carriers. For this reason, CPE does not take place in bulk semiconductors if the energy of the photons is less than the semiconductor energy gap. In superconductors, however, a flow of electrons might be created by spatial phase variations in the wave function, analogous to the Meissner effect, while the system is in thermal equilibrium.

Writing in Physical Review Letters, Anatoly Mal’shukov of the Russian Academy of Science in Troitsk proposes that in a hybrid superconductor-semiconductor system, CPE should be observable even without driving the system out of thermal equilibrium. The model system consists of a semiconductor and superconductor layer, with a doped quantum well between them. The semiconductor is thus subject to both illumination and proximity-induced superconducting coherence effects. The resulting Cooper pair correlations induced in the semiconductor yield a dc current, which, unlike in a pure semiconductor, is not due to a shift of the electron distribution from the thermal equilibrium. The proposed effect has implications not only for spintronics but also for topological superconductors, since the setup studied has been considered as a key element in recent studies of these. – Daniel Ucko


Announcements

More Announcements »

Subject Areas

OpticsSuperconductivitySemiconductor Physics

Previous Synopsis

Quantum Information

A Traffic Light for Photons

Read More »

Next Synopsis

Related Articles

Viewpoint: Chasing the Exciton Condensate
Semiconductor Physics

Viewpoint: Chasing the Exciton Condensate

Unusual interactions between charges have been observed in two closely separated graphene bilayers, a promising system in which to create a condensate of electron-hole pairs. Read More »

Focus: Detecting Photons With a Thermometer
Mesoscopics

Focus: Detecting Photons With a Thermometer

A new technique detects as few as 200 microwave photons at a time by the heat they supply to an electrical circuit. Read More »

Viewpoint: Squeezed Light Reengineers Resonance Fluorescence
Atomic and Molecular Physics

Viewpoint: Squeezed Light Reengineers Resonance Fluorescence

By bathing a superconducting qubit in squeezed light, researchers have been able to confirm a decades-old prediction for the resulting phase-dependent spectrum of resonance fluorescence. Read More »

More Articles