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2005

Fermionic Mach-Zehnder interferometer subject to a quantum bath

Fermionic Mach-Zehnder interferometer subject to a quantum bath

F Marquardt

EPL 72 (5) 788-794 (2005) | Journal | PDF

We study fermions in a Mach-Zehnder interferometer, subject to a quantum-mechanical environment leading to inelastic scattering, decoherence, renormalization effects, and time-dependent conductance fluctuations. We present a method to derive both the loss of interference contrast as well as the shot noise, using equations of motion and leading-order perturbation theory. The dependence of the shot noise on the Aharonov-Bohm phase acquires an unexpected average phase shift, due to correlations between the fluctuating renormalized phase shift and the output current. We discuss the limiting behaviours at low and high voltages, compare with simpler models of dephasing, and present implications for experiments.

Many-fermion generalization of the Caldeira-Leggett model

Many-fermion generalization of the Caldeira-Leggett model

F Marquardt, D S Golubev

Physical Review A 72 (2) 022113 (2005) | Journal | PDF

We analyze a model system of fermions in a harmonic oscillator potential under the influence of a dissipative environment: The fermions are subject to a fluctuating force deriving from a bath of harmonic oscillators. This represents an extension of the well-known Caldeira-Leggett model to the case of many fermions. Using the method of bosonization, we calculate one- and two-particle Green's functions of the fermions. We discuss the relaxation of a single extra particle added above the Fermi sea, considering also dephasing of a particle added in a coherent superposition of states. The consequences of the separation of center-of-mass and relative motion, the Pauli principle, and the bath-induced effective interaction are discussed. Finally, we extend our analysis to a more generic coupling between system and bath, which results in complete thermalization of the system.

Spin relaxation in a quantum dot due to Nyquist noise

Spin relaxation in a quantum dot due to Nyquist noise

F Marquardt, VA Abalmassov

Physical Review B 71 (16) 165325 (2005) | Journal | PDF

We calculate electron and nuclear spin relaxation rates in a quantum dot due to the combined action of Nyquist noise and electron-nuclei hyperfine or spin-orbit interactions. The relaxation rate is linear in the resistance of the gate circuit and, in the case of spin-orbit interaction, it depends essentially on the orientations of both the static magnetic field and the fluctuating electric field, as well as on the ratio between Rashba and Dresselhaus interaction constants. We provide numerical estimates of the relaxation rate for typical system parameters, compare our results with other, previously discussed mechanisms, and show that the Nyquist mechanism can have an appreciable effect for experimentally relevant systems.

Contact

Theory Division
Prof. Florian Marquardt

Max Planck Institute for the Science of Light
Staudtstr. 2
91058 Erlangen, Germany

For all general inquiries, please contact us at:

florian.marquardt@mpl.mpg.de
anna-gesine.murphy@mpl.mpg.de

Tel: +49 9131 7133 401
Fax: +49 9131 7133 409

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