Separation-dependent localization in a two-impurity spin-boson model

Dara P S McCutcheon, Ahsan Nazir, Sougato Bose, Andrew J. Fisher

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    Using a variational approach we investigate the delocalized to localized crossover in the ground state of an Ohmic two-impurity spin-boson model, describing two otherwise noninteracting spins coupled to a common bosonic environment. We show that a competition between an environment-induced Ising spin interaction and externally applied fields leads to variations in the system-bath coupling strength, αc, at which the delocalized-localized crossover occurs. Specifically, the crossover regime lies between αc =0.5 and αc =1 depending upon the spin separation and the strength of the transverse tunneling field. This is in contrast to the analogous single-spin case, for which the crossover occurs (in the scaling limit) at fixed αc = 1. We also discuss links between the two-impurity spin-boson model and a dissipative two-spin transverse Ising model, showing that the latter possesses the same qualitative features as the Ising strength is varied. Finally, we show that signatures of the crossover may be observed in single impurity observables, as well as in the behavior of the system-environment entanglement. © 2010 The American Physical Society.
    Original languageEnglish
    Article number235321
    JournalPhysical Review B - Condensed Matter and Materials Physics
    Issue number23
    Publication statusPublished - 18 Jun 2010

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