Excitation Spectrum of a Double Quantum Well System

TL;DR

This paper analyzes the collective charge-excitation spectrum of a double quantum well system under strong magnetic fields, revealing how magnetic field variations influence excitation velocity and phase boundaries in quantum Hall states.

Contribution

It provides a first-order correction to the excitation spectrum considering finite magnetic field effects within the random phase approximation.

Findings

Dependence of excitation velocity on magnetic field

Identification of phase boundary via roton minimum softening

Quantitative spectrum analysis in strong magnetic fields

Abstract

The collective charge-excitation spectrum of a double quantum well system in a strong magnetic field is obtained within the random phase approximation. Correction to the spectrum coming from the finiteness of the magnetic field is calculated up to the first order in inverse of the magnetic field. Dependencies on the magnetic field of (i) the velocity of long wave length excitation and (ii) the phase boundary of the quantum Hall state signaled by the softening of the roton minimum of the spectrum are discussed. Keywords: quantum Hall effect, two dimensional electrons, strong magnetic field, double quantum well, excitonic state