Localized plasmons in point contacts

TL;DR

This paper proposes that localized plasmons can form near point contact constrictions, potentially explaining conductance deviations from quantization observed experimentally, with a model linking these effects to plasmon excitation energies.

Contribution

It introduces a hydrodynamic model predicting localized plasmons in point contacts and relates these to conductance anomalies through a theoretical framework.

Findings

Localized plasmons likely exist near the constriction.

Conductance deviations show activated temperature dependence.

Activation temperature correlates with plasmon excitation energy.

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(-T_a/T), with a density dependent activation temperature T_a of the order of 2 K. We suggest that T_a 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.