Quantum Oscillations of Photocurrents in HgTe Quantum Wells with Dirac and Parabolic Dispersions

TL;DR

This paper reports the observation and modeling of quantum oscillations in photocurrents induced by terahertz radiation in HgTe quantum wells with different band structures, revealing the role of Landau levels and spin effects.

Contribution

It introduces a microscopic model explaining magneto-oscillations of photocurrent and demonstrates their relation to Landau level crossings and spin polarization in HgTe quantum wells.

Findings

Quantum oscillations of photocurrent are observed in HgTe quantum wells.

The oscillations are caused by Landau level crossings affecting spin polarization.

Photocurrent direction reverses with magnetic field variation.

Abstract

We report on the observation of magneto-oscillations of terahertz radiation induced photocurrent in HgTe/HgCdTe quantum wells (QWs) of different widths, which are characterized by a Dirac-like, inverted and normal parabolic band structure. The photocurrent data are accompanied by measurements of photoresistance (photoconductivity), radiation transmission, as well as magneto-transport. We develop a microscopic model of a cyclotron-resonance assisted photogalvanic effect, which describes main experimental findings. We demonstrate that the quantum oscillations of the photocurrent are caused by the crossing of Fermi level by Landau levels resulting in the oscillations of spin polarization and electron mobilities in spin subbands. Theory explains a photocurrent direction reversal with the variation of magnetic field observed in experiment. We describe the photoconductivity oscillations related with the thermal suppression of the Shubnikov-de Haas effect.