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.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.

arXiv:1801.04594Physical review. B./Physical review. BJun 11, 201813 citations

Transport as a sensitive indicator of quantum criticality

G Schaller, Malte Vogl, Tobias Brandes

We consider bosonic transport through one-dimensional spin systems. Transport is induced by coupling the spin systems to bosonic reservoirs kept at different temperatures. In the limit of weak-coupling between spins and bosons we apply the quantum-optical master equation to calculate the energy transmitted from source to drain reservoirs. At large thermal bias, we find that the current for longitudinal transport becomes independent of the chain length and is also not drastically affected by the presence of disorder. In contrast, at small temperatures, the current scales inversely with the chain length and is further suppressed in the presence of disorder. We also find that the critical behaviour of the ground state is mapped to critical behaviour of the current--even in configurations with infinite thermal bias.We consider bosonic transport through one-dimensional spin systems. Transport is induced by coupling the spin systems to bosonic reservoirs kept at different temperatures. In the limit of weak-coupling between spins and bosons we apply the quantum-optical master equation to calculate the energy transmitted from source to drain reservoirs. At large thermal bias, we find that the current for longitudinal transport becomes independent of the chain length and is also not drastically affected by the presence of disorder. In contrast, at small temperatures, the current scales inversely with the chain length and is further suppressed in the presence of disorder. We also find that the critical behaviour of the ground state is mapped to critical behaviour of the current--even in configurations with infinite thermal bias.

arXiv:1403.7611Journal of Physics Condensed MatterMay 22, 20146 citations

Heat transport in quantum spin chains

Carlos Mejía-Monasterio, Hannu Christian Wichterich

arXiv:0709.1412The European Physical Journal Special TopicsDec 1, 200736 citations

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.