Spin-orbit coupled spin-boson model : A variational analysis

TL;DR

This paper extends the spin-boson model to include spin-orbit coupling and analyzes the resulting quantum dissipation effects using a variational approach, revealing localization and phase transitions relevant for quantum information.

Contribution

It introduces a generalized spin-orbit coupled spin-boson model and applies a variational method to uncover localization and phase transition phenomena.

Findings

Localization transition with spectrum change

Continuous and discontinuous phase transitions

Entanglement entropy as a transition marker

Abstract

The spin-boson (SB) model is a standard prototype for quantum dissipation, which we generalize in this work, to explore the dissipative effects on a one-dimensional spin-orbit (SO) coupled particle in the presence of a sub-ohmic bath. We analyze this model by extending the well-known variational polaron approach, revealing a localization transition accompanied by an intriguing change in the spectrum, for which the doubly degenerate minima evolves to a single minimum at zero momentum as the system-bath coupling increases. For translational invariant system with conserved momentum, a continuous magnetization transition occurs, whereas the ground state changes discontinuously. We further investigate the transition of the ground state in the presence of harmonic confinement, which effectively models a quantum dot-like nanostructure under the influence of the environment. In both the scenarios, the entanglement entropy of the spin-sector can serve as a marker for these transitions. Interestingly, for the trapped system, a cat-like superposition state corresponds to maximum entanglement entropy below the transition, highlighting the relevance of the present model for studying the effect of decoherence on intra-particle entanglement in the context of quantum information processing.