Spin entanglement via STM current

TL;DR

This paper models a two-spin system under STM bias, revealing how tunneling induces exchange interactions and entanglement, with implications for spin resonance and quantum information.

Contribution

It derives a master equation showing tunneling-induced exchange and Dzyaloshinskii-Moriya interactions, and demonstrates significant spin entanglement via dark states.

Findings

Tunneling generates exchange and Dzyaloshinskii-Moriya interactions.

Dark states with zero decay rate enable spin entanglement.

Electronic environment induces notable spin-spin entanglement.

Abstract

We consider a system of two spins under a scanning tunneling microscope bias and derive its master equation. We find that the tunneling elements to the electronic contacts (tip and substrate) generate an exchange interaction between the spins, as well as a Dzyaloshinskii-Moriya interaction in the presence of spin-orbit coupling. The tunnel current spectrum then shows additional lines compared to conventional spin resonance experiments. When the spins have degenerate Larmor frequencies and equal tunneling amplitudes (without spin-orbit), there is a dark state with vanishing decay rate. The coupling to the electronic environment generates significant spin-spin entanglement via the dark state, even if the initial state is non-entangled.