Cyclotron effect on coherent spin precession of two-dimensional electrons

TL;DR

This study explores how cyclotron motion influences the coherent spin precession of high-mobility two-dimensional electrons in GaAs/AlGaAs quantum wells, revealing effects dependent on crystal orientation and magnetic fields.

Contribution

It demonstrates the impact of cyclotron motion on spin dynamics and provides a theoretical model explaining orientation-dependent effects in quantum wells.

Findings

Cyclotron motion causes fast oscillations in spin polarization.

Spin dephasing time increases significantly due to cyclotron effects.

Orientation of quantum wells affects the spin-orbit interaction and resulting spin dynamics.

Abstract

We investigate the spin dynamics of high-mobility two-dimensional electrons in GaAs/AlGaAs quantum wells grown along the $[001]$ and $[110]$ directions by time-resolved Faraday rotation at low temperatures. In measurements on the $(001)$-grown structures without external magnetic fields, we observe coherent oscillations of the electron spin polarization about the effective spin-orbit field. In non-quantizing magnetic fields applied normal to the sample plane, the cyclotron motion of the electrons rotates the effective spin-orbit field. This rotation leads to fast oscillations in the spin polarization about a non-zero value and a strong increase in the spin dephasing time in our experiments. These two effects are absent in the $(110)$-grown structure due to the different symmetry of its effective spin-orbit field. The measurements are in excellent agreement with our theoretical model.