Quantum frustration of dissipation by a spin bath

Hackl²,

Kehrein

2013

Phys. Rev. B

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Using flow equations and equilibrium and nonequilibrium dynamics of a two-level system (TLS) is investigated, which couples Ohmically via noncommuting components to two independent oscillator baths. In equilibrium, the two-level energy splitting is protected when the TLS is coupled symmetrically to both baths. A critical asymmetry angle separates the localized from the delocalized phase. Real-time decoherence of a nonequilibrium initial state is studied as well. The short-time dynamics exhibits initial slips on the scale of the cutoff frequency of the bath modes. Moreover, whereas for a single bath decay of coherence depends crucially on the chosen initial state, for a symmetric coupling to two baths this dependence vanishes.

Section: Introductionmentioning

confidence: 99%

Nonequilibrium dynamics of a system with quantum frustration

Hackl²,

Kehrein

2013

Phys. Rev. B

Self Cite

“…Recently a certain class of dissipative quantum systems has aroused interest, where the system couples to two heat baths through non-commuting variables [9][10][11][12][13][14][15]. In Refs.…”

mentioning

confidence: 99%

“…In Refs. [9,10,15] a spin was considered which couples to two independent oscillator baths. In Refs.…”

mentioning

confidence: 99%

Minimal coupling in oscillator models of quantum dissipation

Physica A: Statistical Mechanics and its Applications

Sols

2013

The dissipative harmonic oscillator has two representations. In the first representation the central oscillator couples with its position to an oscillator bath. In the second one it couples with its momentum to the bath. Both representations are related by a unitary transformation. If the central oscillator couples with its position and momentum to two independent baths, no such unitary transformation exists. We discuss two possible models of this type and their physical relevance

“…These cancellations were indeed observed in a variety of dierent systems as a two-level system (TLS) coupled to two oscillator bath [1417] or to two spin--baths [18], a harmonic oscillator coupled to two oscillator bath [1922] in spin-lattices [23] or the Josephson networks [24]. The relation to two channel Kondo physics was already pointed out in [14,25,26].…”

Section: The 2 Bath Two Level System (2btls)mentioning

confidence: 90%

Asymmetry Induced Localization

2013

Acta Phys. Pol. A

We consider a two-level system, which couples via non-commuting operators to two independent oscillator baths. When the coupling is symmetric, the renormalized hopping matrix element is nite even for innitely strong coupling strength. The two-level system is in a delocalized phase. For nite coupling strength a localization transition occurs for a critical asymmetry angle, which separates the localized from the delocalized phase. Using the method of ow equations we are able to monitor real time dynamics.