Far-infrared absorption in parallel quantum wires with weak tunneling

TL;DR

This paper investigates how weak tunneling between coupled quantum wires affects their absorption spectrum, revealing additional peaks, shifts, and magnetic field effects on excitations and plasmon damping.

Contribution

It demonstrates the impact of weak tunneling on intersubband excitations and absorption spectra in coupled quantum wires, including magnetic field interactions.

Findings

Additional peaks from single-particle excitations appear due to tunneling.

Main absorption peak shifts due to depolarization effects.

Strong magnetic fields cause damping of intersubband plasmons.

Abstract

We study collective and single-particle intersubband excitations in a system of quantum wires coupled via weak tunneling. For an isolated wire with parabolic confinement, the Kohn's theorem guarantees that the absorption spectrum represents a single sharp peak centered at the frequency given by the bare confining potential. We show that the effect of weak tunneling between two parabolic quantum wires is twofold: (i) additional peaks corresponding to single-particle excitations appear in the absorption spectrum, and (ii) the main absorption peak acquires a depolarization shift. We also show that the interplay between tunneling and weak perpendicular magnetic field drastically enhances the dispersion of single-particle excitations. The latter leads to a strong damping of the intersubband plasmon for magnetic fields exceeding a critical value.