Spin relaxation dynamics of quasiclassical electrons in ballistic quantum dots with strong spin-orbit coupling

TL;DR

This study investigates spin relaxation in ballistic quantum dots with strong spin-orbit coupling, revealing distinct behaviors in chaotic versus regular systems and highlighting limitations of semiclassical simulations.

Contribution

It provides a comparative analysis of classical and quantum spin dynamics in quantum dots, emphasizing differences in relaxation behavior based on system chaos.

Findings

Spin polarization relaxes to zero in chaotic dots, contradicting quantum predictions.

In regular dots, spin evolves to a residual value, matching quantum results.

Semiclassical simulations miss long-term mesoscopic echo effects.

Abstract

We performed path integral simulations of spin evolution controlled by the Rashba spin-orbit interaction in the semiclassical regime for chaotic and regular quantum dots. The spin polarization dynamics have been found to be strikingly different from the D'yakonov-Perel' (DP) spin relaxation in bulk systems. Also an important distinction have been found between long time spin evolutions in classically chaotic and regular systems. In the former case the spin polarization relaxes to zero within relaxation time much larger than the DP relaxation, while in the latter case it evolves to a time independent residual value. The quantum mechanical analysis of the spin evolution based on the exact solution of the Schroedinger equation with Rashba SOI has confirmed the results of the classical simulations for the circular dot, which is expected to be valid in general regular systems. In contrast, the spin relaxation down to zero in chaotic dots contradicts to what have to be expected from quantum mechanics. This signals on importance at long time of the mesoscopic echo effect missed in the semiclassical simulations.