Charge Relaxation and Dephasing in Coulomb Coupled Conductors

TL;DR

This paper investigates how Coulomb interactions cause charge fluctuations that lead to dephasing in coupled mesoscopic conductors, relating phase-breaking times to transport coefficients and illustrating with a quantum point contact and quantum dot system.

Contribution

It introduces a theoretical framework linking dephasing time to capacitance and charge relaxation resistances in Coulomb-coupled conductors, including non-equilibrium effects.

Findings

Dephasing time is related to charge relaxation resistance and capacitance.

Charge fluctuations due to Coulomb interactions cause phase decoherence.

The model is exemplified with a quantum point contact near a quantum dot.

Abstract

The dephasing time in coupled mesoscopic conductors is caused by the fluctuations of the dipolar charge permitted by the long range Coulomb interaction. We relate the phase breaking time to elementary transport coefficients which describe the dynamics of this dipole: the capacitance, an equilibrium charge relaxation resistance and in the presence of transport through one of the conductors a non-equilibrium charge relaxation resistance. The discussion is illustrated for a quantum point contact in a high magnetic field in proximity to a quantum dot.