Long-range magnetic response of theXYspin chain under far-from-equilibrium conditions

Abstract

Within the formalism of the Keldysh Green's functions we investigate long-range response of an anisotropic XY chain to the local magnetic field. This field couples to a single spin on a selected lattice site. The system is driven out of equilibrium by a coupling to two semi-infinite XX spin chains. We demonstrate that the longrange response becomes enhanced by a few orders of magnitude upon application of nonequilibrium conditions. This enhancement does not occur in the isotropic XX chain. Our results agree with the recently predicted nonequilibrium-driven long-range magnetic correlations ͓T. Prosen and I. Pižorn, Phys. Rev. Lett. 101, 105701 ͑2008͔͒. We argue that this effect may be observed in quasi-one-dimensional triplet superconductors.

Explicit solution of the Lindblad equation for nearly isotropic boundary drivenXYspin 1/2 chain

“…In this paper we show that the non-equilibrium transition can be explained with explicit analytical calculation in the special regime of small anisotropy, where perturbation theory in the anisotropy parameter can be successfully applied. We note that the small anisotropy open XY chain has recently also been studied numerically in terms of the Keldysh formalism [19], where the non-equilibrium phase transition has been re-confirmed.…”

Current-driven defect-unbinding transition in anXYferromagnet

“…6 In some models, excitations propagate ballistically so the concept of effective temperature does not apply and nonequilibrium phase transitions arise for different reasons. 2,9,14 In this paper we investigate an alternative route to nonequilibrium quantum criticality. We show that in continuous-symmetry magnets an applied current can lead to a current-driven defect unbinding.…”

“…Examples include phase transitions induced at temperature T =0 in the presence of a nonequilibrium drive [1][2][3][4][5][6] as well as quantum coarsening and quench problems of a system prepared or maintained in a far-from equilibrium state. [7][8][9][10][11] In many of the cases of nonequilibrium quantum criticality studied to date, the dominant physics is that the nonequilibrium drive acts to produce a noise term (typically delta-correlated at long scales) in the equation of motion for the critical fluctuations. 1 This noise term increases fluctuations and destroys order, similarly to temperature.…”

Theory of quantum energy transfer in spin chains: Superexchange and ballistic motion

“…mechanism. This was done in the context of vibrational energy transfer [16] and thermal transport in spin chain [17][18][19], for both classical and quantum systems, using, e.g., molecular dynamics simulations [16], the quantum master equation method [19][20][21], the Green-Kubo formula [22,23],…”

“…This was done in the context of vibrational energy transfer [16] and thermal transport in spin chain [17][18][19], for both classical and quantum systems, using, e.g., molecular dynamics simulations [16], the quantum master equation method [19][20][21], the Green-Kubo formula [22,23], and the density matrix renormalization group method [24]. In the off-resonant regime simula-tions on purely harmonic systems indicated on a tunneling dynamics of heat transfer [10].…”