Manifestation of the Hofstadter butterfly in far-infrared absorption

TL;DR

This paper demonstrates how the Hofstadter butterfly spectrum manifests in far-infrared absorption measurements of a modulated two-dimensional electron gas under magnetic fields, revealing complex plasmon modes.

Contribution

It provides a self-consistent calculation showing the emergence of Hofstadter butterfly features in absorption spectra, linking spectral peaks to electron density and subband structure.

Findings

Hofstadter butterfly features appear in absorption spectra under strong modulation.

Absorption peak structure depends on chemical potential and electron density.

Intra- and intersubband magnetoplasmon modes reflect the subband structure.

Abstract

The far-infrared absorption of a two-dimensional electron gas with a square-lattice modulation in a perpendicular constant magnetic field is calculated self-consistently within the Hartree approximation. For strong modulation and short period we obtain intra- and intersubband magnetoplasmon modes reflecting the subbands of the Hofstadter butterfly in two or more Landau bands. The character of the absorption and the correlation of the peaks to the number of flux quanta through each unit cell of the periodic potential depends strongly on the location of the chemical potential with respect to the subbands, or what is the same, on the density of electrons in the system.