Giant spin-polarized current in a Dirac fermion system at cyclotron resonance

TL;DR

This study demonstrates a giant, tunable, spin-polarized photocurrent in a Dirac fermion system within HgTe/HgCdTe quantum wells, driven by cyclotron resonance and confirmed through multiple experimental techniques.

Contribution

It provides the first observation of a giant, tunable, spin-polarized photocurrent in a Dirac fermion system at cyclotron resonance, supported by a developed theoretical model.

Findings

Resonant photocurrent observed at specific magnetic fields.

Photocurrent can be tuned via optical gating.

Theoretical model explains spin polarization and scattering mechanisms.

Abstract

We report on the observation of the giant spin-polarized photocurrent in HgTe/HgCdTe quantum well (QW) of critical thickness at which a Dirac spectrum emerges. Exciting QW of 6.6 nm width by terahertz (THz) radiation and sweeping magnetic field we detected a resonant photocurrent. Remarkably, the position of the resonance can be tuned from negative (-0.4 T) to positive (up to 1.2 T) magnetic fields by means of optical gating. The photocurent data, accompanied by measurements of radiation transmission as well as Shubnikov-de Haas and quantum Hall effects, give an evidence that the enhancement of the photocurrent is caused by cyclotron resonance in a Dirac fermion system. The developed theory shows that the current is spin polarized and originates from the spin dependent scattering of charge carriers heated by the radiation.