Semiclassical transport in nearly symmetric quantum dots. I. Symmetry breaking in the dot

Whitney, Robert S. and Schomerus, Henning and Kopp, Marten (2009) Semiclassical transport in nearly symmetric quantum dots. I. Symmetry breaking in the dot. Physical Review E, 80 (5). 056209. ISSN 1539-3755

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We apply the semiclassical theory of transport to quantum dots with exact and approximate spatial symmetries; left-right mirror symmetry, up-down mirror symmetry, inversion symmetry, or fourfold symmetry. In this work—the first of a pair of articles—we consider (a) perfectly symmetric dots and (b) nearly symmetric dots in which the symmetry is broken by the dot's internal dynamics. The second article addresses symmetry-breaking by displacement of the leads. Using semiclassics, we identify the origin of the symmetry-induced interference effects that contribute to weak localization corrections and universal conductance fluctuations. For perfect spatial symmetry, we recover results previously found using the random-matrix theory conjecture. We then go on to show how the results are affected by asymmetries in the dot, magnetic fields, and decoherence. In particular, the symmetry-asymmetry crossover is found to be described by a universal dependence on an asymmetry parameter gamma_asym. However, the form of this parameter is very different depending on how the dot is deformed away from spatial symmetry. Symmetry-induced interference effects are completely destroyed when the dot's boundary is globally deformed by less than an electron wavelength. In contrast, these effects are only reduced by a finite amount when a part of the dot's boundary smaller than a lead-width is deformed an arbitrarily large distance.

Item Type:
Journal Article
Journal or Publication Title:
Physical Review E
Uncontrolled Keywords:
?? statistical and nonlinear physicsstatistics and probabilitycondensed matter physicsqc physics ??
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Deposited On:
07 Dec 2009 09:22
Last Modified:
11 Apr 2024 00:16