Quantum spin circulator in Y junctions of Heisenberg chains

TL;DR

This paper demonstrates the theoretical possibility of creating a quantum spin circulator in Y junctions of Heisenberg chains, enabling nonreciprocal spin current routing without charge transport, which could facilitate chiral spin liquid phases.

Contribution

It introduces a novel approach to realize a quantum spin circulator using chiral three-spin interactions in Y junctions of Heisenberg chains, supported by analytical and numerical methods.

Findings

A chiral fixed point with asymmetric spin conductance is identified.

The system exhibits a transition from disconnected chains to a Kondo-like regime.

Networks of such junctions could realize chiral spin liquid phases.

Abstract

We show that a quantum spin circulator, a nonreciprocal device that routes spin currents without any charge transport, can be achieved in Y junctions of identical spin-$1/2$ Heisenberg chains coupled by a chiral three-spin interaction. Using bosonization, boundary conformal field theory, and density-matrix renormalization group simulations, we find that a chiral fixed point with maximally asymmetric spin conductance arises at a critical point separating a regime of disconnected chains from a spin-only version of the three-channel Kondo effect. We argue that networks of spin-chain Y junctions provide a controllable approach to construct long-sought chiral spin liquid phases.