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.
@article{arxiv.1801.04594,
title = {Quantum spin circulator in Y junctions of Heisenberg chains},
author = {F. Buccheri and R. Egger and R. G. Pereira and F. B. Ramos},
journal= {arXiv preprint arXiv:1801.04594},
year = {2018}
}