Quantum spin dimers from chiral dissipation in cold-atom chains

Ramos, Tomás and Pichler, Hannes and Daley, Andrew J. and Zoller, Peter (2014) Quantum spin dimers from chiral dissipation in cold-atom chains. Physical Review Letters, 113 (23). ISSN 0031-9007

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    We consider the nonequilibrium dynamics of a driven dissipative spin chain with chiral coupling to a one-dimensional (1D) bosonic bath, and its atomic implementation with a two-species mixture of cold quantum gases. The reservoir is represented by a spin-orbit coupled 1D quasicondensate of atoms in a magnetized phase, while the spins are identified with motional states of a separate species of atoms in an optical lattice. The chirality of reservoir excitations allows the spins to couple differently to left- and right-moving modes, which in our atomic setup can be tuned from bidirectional to purely unidirectional. Remarkably, this leads to a pure steady state in which pairs of neighboring spins form dimers that decouple from the remainder of the chain. Our results also apply to current experiments with two-level emitters coupled to photonic waveguides.