551 research outputs found
History dependence, memory and metastability in electron glasses
We discuss the history dependence and memory effects which are observed in
the out-of-equilibrium conductivity of electron glasses. The experiments can be
understood by assuming that the local density of states retains a memory of the
sample history. We provide analytical arguments for the consistency of this
assumption, and discuss the saturation of the memory effect with increasing
gate voltage change. This picture is bolstered by numerical simulations at zero
temperature, which moreover demonstrate the incompressibility of the Coulomb
glass on short timescales.Comment: 4 pages, 1 figur
Statistical and Computational Tradeoffs in Stochastic Composite Likelihood
Maximum likelihood estimators are often of limited practical use due to the
intensive computation they require. We propose a family of alternative
estimators that maximize a stochastic variation of the composite likelihood
function. Each of the estimators resolve the computation-accuracy tradeoff
differently, and taken together they span a continuous spectrum of
computation-accuracy tradeoff resolutions. We prove the consistency of the
estimators, provide formulas for their asymptotic variance, statistical
robustness, and computational complexity. We discuss experimental results in
the context of Boltzmann machines and conditional random fields. The
theoretical and experimental studies demonstrate the effectiveness of the
estimators when the computational resources are insufficient. They also
demonstrate that in some cases reduced computational complexity is associated
with robustness thereby increasing statistical accuracy.Comment: 30 pages, 97 figures, 2 author
Non-equilibrium conductance of a three-terminal quantum dot in the Kondo regime: Perturbative Renormalization Group
Motivated by recent experiments, we consider a single-electron transistor in
the Kondo regime which is coupled to three leads in the presence of large bias
voltages. Such a steady-state non-equilibrium system is to a large extent
governed by a decoherence rate induced by the current through the dot. As the
two-terminal conductance turns out to be rather insensitive to the decoherence
rate, we study the conductance in a three-terminal device using perturbative
renormalization group and calculate the characteristic splitting of the Kondo
resonance. The interplay between potential biases and anisotropy in coupling to
the three leads determines the decoherence rate and the conditions for strong
coupling.Comment: 4 pages, 4 figure
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