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Effects of a nonlinear bath at low temperatures

Hanno Gassmann·C. Bruder
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Abstract

We use the numerical flow-equation renormalization method to study a nonlinear bath at low temperatures. The model of our nonlinear bath consists of a single two-level system coupled to a linear oscillator bath. The effects of this nonlinear bath are analyzed by coupling it to a spin, whose relaxational dynamics under the action of the bath is studied by calculating spin-spin correlation functions. As a first result, we derive flow equations for a general four-level system coupled to an oscillator bath, valid at low temperatures. We then treat the two-level system coupled to our nonlinear bath as a special case of the dissipative four-level system. We compare the effects of the nonlinear bath with those obtained using an effective linear bath, and study the differences between the two cases at low temperatures.

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Hanno Gassmann, C. Bruder. 2004-11-15. Effects of a nonlinear bath at low temperatures. https://doi.org/10.1103/physrevb.72.035102

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