Energy relaxation rate and its mesoscopic fluctuations in quantum dots

Vladyslav A. Kozii, Mikhail A. Skvortsov

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    5 Citations (Scopus)


    We analyze the applicability of the Fermi-golden-rule description of quasiparticle relaxation in a closed diffusive quantum dot with electron-electron interaction. Assuming that single-particle levels are already resolved but the initial stage of quasiparticle disintegration can still be described by a simple exponential decay, we calculate the average inelastic energy relaxation rate of single-particle excitations and its mesoscopic fluctuations. The smallness of mesoscopic fluctuations can then be used as a criterion for the validity of the Fermi-golden-rule description. Technically, we implement the real-space Keldysh diagram technique, handling correlations in the quasi-discrete spectrum non-perturbatively by means of the non-linear supersymmetric sigma model. The unitary symmetry class is considered for simplicity. Our approach is complementary to the lattice-model analysis of Fock space: though we are not able to describe many-body localization, we derive the exact lowest-order expression for mesoscopic fluctuations of the relaxation rate, making no assumptions on the matrix elements of the interaction. It is shown that for the quasiparticle with the energy ε on top of the thermal state with the temperature T, fluctuations of its energy width become large and the Fermi-golden-rule description breaks down at max{ε,T}~δg, where δ is the mean level spacing in the quantum dot, and g is its dimensionless conductance.

    Original languageEnglish
    Pages (from-to)20-52
    Number of pages33
    JournalAnnals of Physics
    Publication statusPublished - 1 Aug 2016


    • Electron-electron interaction
    • Many-body localization
    • Mesoscopic fluctuations
    • Non-equilibrium system
    • Quantum dot


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