Large Splitting of the Cyclotron Resonance Line in AlGaN/GaN Heterostructures

TL;DR

This study observes large, unexplained splittings in cyclotron resonance lines in AlGaN/GaN heterostructures, indicating strong interactions with unknown excitations and revealing gaps in current understanding of such resonances.

Contribution

It reports the first observation of large CR line splittings in AlGaN/GaN heterostructures across various densities, suggesting novel interactions not previously understood.

Findings

CR line splittings up to 2 meV observed

Splitting energy varies with √n_{2D}

Resembles level anti-crossing phenomena

Abstract

Cyclotron-resonance (CR) measurements on two-dimensional (2D) electrons in AlGaN/GaN heterojunctions reveal large splittings (up to 2 meV) of the CR line for all investigated densities, $n_{2D}$, from 1 to $4\times 10^{12}cm^{-2}$ over wide ranges of magnetic field. The features resemble a level anti-crossing and imply a strong interaction with an unknown excitation of the solid. The critical energy of the splitting varies from 5 to 12 meV and as $\sqrt{n_{2D}}$. The phenomenon resembles data from AlGaAs/GaAs whose origin remains unresolved. It highlights a lack of basic understanding of a very elementary resonance in solids.