Electron focusing, mode spectroscopy and mass enhancement in small GaAs/AlGaAs rings

TL;DR

This paper reports the discovery of a new electron focusing effect in small GaAs/AlGaAs rings, enabling their use as mass spectrometers and revealing a significant magnetic field-dependent increase in electron effective mass.

Contribution

The study introduces a novel electron focusing phenomenon in small rings and demonstrates its application as a mass spectrometer, along with direct measurement of mass enhancement under magnetic fields.

Findings

Electron focusing effect observed in small GaAs/AlGaAs rings.

Effective electron mass increases by a factor of 50 at 0.5T.

Focusing peaks correlate with dispersion relation of subbands.

Abstract

A new electron focusing effect has been discovered in small single and coupled GaAs/AlGaAs rings. The focusing in the single ring is attributed solely to internal orbits. The focusing effect allows the ring to be used as a small mass spectrometer. The focusing causes peaks in the magnetoresistance at low fields, and the peak positions were used to study the dispersion relation of the one-dimensional magnetoelectric subbands. The electron effective mass increases with the applied magnetic field by a factor of $50$, at a magnetic field of $0.5T$. This is the first time this increase has been measured directly. General agreement obtains between the experiment and the subband calculations for straight channels.