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Equilibrium and non-equilibrium dynamics of the sub-ohmic spin-boson model

Frithjof B. Anders·Ralf Bulla·Matthias Vojta
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Abstract

Employing the non-perturbative numerical renormalization group method, we study the dynamics of the spin-boson model, which describes a two-level system coupled to a bosonic bath with spectral density J(omega) propto omega^s. We show that, in contrast to the case of ohmic damping, the delocalized phase of the sub-ohmic model cannot be characterized by a single energy scale only, due to the presence of a non-trivial quantum phase transition. In the strongly sub-ohmic regime, s<<1, weakly damped coherent oscillations on short time scales are possible even in the localized phase - this is of crucial relevance, e.g., for qubits subject to electromagnetic noise.

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Frithjof B. Anders, Ralf Bulla, Matthias Vojta. 2007-05-25. Equilibrium and non-equilibrium dynamics of the sub-ohmic spin-boson model. https://doi.org/10.1103/physrevlett.98.210402

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