Spin polarization induced by decoherence in a tunneling one-dimensional Rashba model

TL;DR

This paper investigates how decoherence and magnetic fields influence spin polarization in tunneling electrons within a one-dimensional Rashba model, revealing conditions under which spin polarization emerges and its relation to time-reversal symmetry breaking.

Contribution

The study provides an exact solution to 1D tunneling models showing how decoherence breaks TRS and induces spin polarization, connecting theoretical predictions with experimental CISS observations.

Findings

Decoherence breaks TRS and induces spin polarization.

Spin polarization aligns with magnetic fields or effective SO fields.

TRS preservation prevents spin polarization regardless of barrier or SO strength.

Abstract

Basic questions on the nature of spin polarization in two terminal systems and the way in which decoherence breaks Time-Reversal Symmetry (TRS) are analyzed. We exactly solve several one-dimensional models of tunneling electrons and show the interplay of spin precession and decay of the wavefunction in either a U(1) magnetic field or an effective Spin-Orbit (SO) magnetic field. Spin polarization is clearly identified as the emergence of a spin component parallel to either magnetic field. We show that Onsager's reciprocity is fulfilled when time reversal symmetry is present and no spin polarization arises, no matter the barrier parameters or the SO strength. Introducing a Buttiker's decoherence probe, that preserves unitarity of time evolution, we show that breaking of TRS results in a strong spin polarization for realistic SO, and barrier strengths. We discuss the significance of these results as a very general scenario for the onset of the Chiral-Induced Spin Selectivity effect (CISS), now possibly matching experiments in a quantitative manner.