Synthetic spin-orbit coupling mediated by a bosonic environment

TL;DR

This paper investigates how a bosonic environment can induce a phonon-mediated spin-orbit coupling in a quantum impurity confined to a ring, revealing a transition from non-interacting to strongly interacting states with potential applications in spintronics.

Contribution

It introduces the concept of phonon-mediated spin-orbit coupling in a rotating polaron system and analyzes its behavior across different interaction regimes.

Findings

Coupling between internal and orbital angular momenta emerges due to phonon exchange.

A sharp transition occurs at a critical coupling strength, indicated by a kink in the correlation function.

The results suggest potential applications in spintronics and topological insulators.

Abstract

We study a mobile quantum impurity, possessing internal rotational degrees of freedom, confined to a ring in the presence of a many-particle bosonic bath. By considering the recently introduced rotating polaron problem, we define the Hamiltonian and examine the energy spectrum. The weak-coupling regime is studied by means of a variational ansatz in the truncated Fock space. The corresponding spectrum indicates that there emerges a coupling between the internal and orbital angular momenta of the impurity as a consequence of the phonon exchange. We interpret the coupling as a phonon-mediated spin-orbit coupling and quantify it by using a correlation function between the internal and orbital angular momentum operators. The strong-coupling regime is investigated within the Pekar approach and it is shown that the correlation function of the ground state shows a kink at a critical coupling, that is explained by a sharp transition from the non-interacting state to the states that exhibit strong interaction with the surroundings. The results might find applications in such fields as spintronics or topological insulators, where spin-orbit coupling is of crucial importance.