Zero-temperature geometric spin dephasing on a ring in the presence of an Ohmic environment

¹ Department of Physics, Ben Gurion university - Beer Sheva 84105 Israel
² CNRS-Laboratoire de Physique Théorique de l'Ecole Normale Supérieure - 24 rue Lhomond, F-75231 Cedex 05, Paris, France, EU
³ Freie Universität Berlin, Fachbereich Physik - Arnimallee 14, D-14195 Berlin, Germany, EU
⁴ Theoretical Physics Department, Budapest University of Technology and Economics - Budafoki ut 8, H-1521, Budapest, Hungary, EU

^a zarand@phy.bme.hu

Received: 8 April 2011
Accepted: 14 July 2011

Abstract

We study zero-temperature spin dynamics of a particle confined to a ring in the presence of spin-orbit coupling and Ohmic electromagnetic fluctuations. We show that the dynamics of the angular position θ(t) are decoupled from the spin dynamics and that the latter is mapped to certain correlations of a spinless particle. We find that the spin correlations in the z-direction (perpendicular to the ring) are finite at long times, i.e. do not dephase. The parallel (in-plane) components for spin do not dephase at weak dissipation but they probably decay as a power law with time at strong dissipation.