Pure spin decoherence in quantum dots

TL;DR

This paper identifies two microscopic mechanisms causing pure spin decoherence in quantum dots, involving spin-orbit coupling and phonon interactions, with decoherence rates proportional to temperature.

Contribution

It introduces new physical models for spin decoherence in quantum dots, highlighting mechanisms distinct from traditional Dresselhaus and Rashba effects.

Findings

Decoherence arises from spin-orbit coupling to phonons in 2D hole gases.

Decoherence due to spin-dependent phonon coupling in atom chain QDs.

Decoherence rate is linear in temperature in both cases.

Abstract

We uncover two microscopic physical settings with significant pure spin decoherence. First, for quantum dots (QD) electrostatically confined in two-dimensional hole gas, decoherence comes from qubit spin-orbit (SO) coupling to phonons, whose decay due to free charge carriers in contacts is described by Ohmic weighted phonon spectral function. We derive significant SO interactions affecting holes with origin and symmetry distinct from that of conventionally considered Dresselhaus and Rashba terms. In the second setting of electron or hole QDs coupled to a linear chain of atoms, decoherence is due to spin-dependent coupling to phonons, whose decay due to scattering off the free ends of a chain is described by the weighted phonon spectral function inverse proportional to frequency. The decoherence rate in both settings is linear in temperature.