Terahertz magneto-optical spectroscopy of two-dimensional hole and electron systems

TL;DR

This study employs terahertz magneto-optical spectroscopy to explore cyclotron resonance in high mobility 2D electron and hole systems, revealing distinct behaviors due to band structure effects and demonstrating the technique's applicability to 2D hole gases.

Contribution

First application of THz magneto-optical spectroscopy to investigate cyclotron resonance in two-dimensional hole gases, highlighting nonlinear effects from complex valence band structures.

Findings

Linear cyclotron frequency variation in 2DEG with magnetic field

Nonlinear cyclotron frequency in 2DHG due to band structure

Observation of long-lived coherent oscillations (~20 ps)

Abstract

We have used terahertz (THz) magneto-optical spectroscopy to investigate the cyclotron resonance in high mobility two-dimensional electron and hole systems. Our experiments reveal long-lived (~20 ps) coherent oscillations in the measured signal in the presence of a perpendicular magnetic field. The cyclotron frequency extracted from the oscillations varies linearly with magnetic field for a two-dimensional electron gas (2DEG), as expected. However, we find that the complex non-parabolic valence band structure in a two-dimensional hole gas (2DHG) causes the cyclotron frequency and effective mass to vary nonlinearly with the magnetic field, as verified by multiband Landau level calculations. This is the first time that THz magneto-optical spectroscopy has been used to study 2DHG, and we expect that these results will motivate further studies of these unique 2D nanosystems.