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Localized plasmons in point contacts

Henrik Bruus, Karsten Flensberg

cond-mat.mes-hallarXiv:cond-mat/9807342

Abstract

Using a hydrodynamic model of the electron fluid in a point contact geometry we show that localized plasmons are likely to exist near the constriction. We attempt to relate these plasmons with the recent experimental observation of deviations of the quantum point contact conductance from ideal integer quantization. As a function of temperature this deviation exhibits an activated behavior, exp(-Ta/T), with a density dependent activation temperature Ta of the order of 2 K. We suggest that Ta can be identified with the energy needed to excite localized plasmons, and we discuss the conductance deviations in terms of a simple theoretical model involving quasiparticle lifetime broadening due to coupling to the localized plasmons.

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