Condensed Matter Seminar Series

 Pedro Ribeiro

University of Lisbon

Topic:  Bias-driven symmetry-breaking phase transitions in chains of spins or bosons

Far-from-equilibrium quantum states are routinely realized in mesoscopic solid-state devices and recently have also become available in cold atomic gas settings. However, non-equilibrium quantum matter remains a particularly hard topic in the presence of interactions. In this talk, I will give an account of some recent progress in studying the steady-state of spin and hard-core bosonic chains, set out-of-equilibrium by a magnetization or a chemical potential bias, respectively. Specifically, for a transverse field Ising chain, we observed a mixed-order symmetry-breaking quantum phase transition, characterized by a discontinuous jump of the magnetic order parameter concomitant with a divergence of the correlation length. In the bosonic case, we found that any bias destroys the equilibrium quasi-long-range-order. However, the properties of the ensuing steady-state, even in the zero-bias limit, can only be obtained in a non-equilibrium setup.  These findings show that out-of-equilibrium conditions allow for novel critical phenomena not possible at equilibrium. 



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