Exponential sensitivity to dephasing of electrical conduction through a quantum dot

Tworzydlo, J.; Tajic, A.; Schomerus, H.; Brouwer, P. W.; Beenakker, C. W. J.

Exponential sensitivity to dephasing of electrical conduction through a quantum dot

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Description

According to random-matrix theory, interference effects in the conductance of a ballistic chaotic quantum dot should vanish $\propto(τ_ϕ/τ_{D})^{p}$ when the dephasing time $τ_ϕ$ becomes small compared to the mean dwell time $τ_{D}$. Aleiner and Larkin have predicted that the power law crosses over to an exponential suppression $\propto\exp(-τ_{E}/τ_ϕ)$ when $τ_ϕ$ drops below the Ehrenfest time $τ_{E}$. We report the first observation of this crossover in a computer simulation of universal conductance fluctuations. Their theory also predicts an exponential suppression $\propto\exp(-τ_{E}/τ_{D})$ in the absence of dephasing -- which is not observed. We show that the effective random-matrix theory proposed previously for quantum dots without dephasing explains both observations.
4 pages, 4 figures