Magneto-electrical subbands of freely suspended quantum point contacts

TL;DR

This paper introduces a versatile design for freely suspended quantum point contacts with large subband energies, enabling detailed exploration of quantum effects like Landau quantization and spin gaps.

Contribution

The work presents a novel fabrication method for quantum point contacts with high subband energies, facilitating advanced transport spectroscopy studies.

Findings

Large subband energies up to 10meV enable wide magnetic field exploration.

Observation of a large exchange-split spin-gap in Landau levels.

Capacitive control of quantum point contacts via in-plane gates.

Abstract

We present a versatile design of freely suspended quantum point contacts with particular large one-dimensional subband quantization energies of up to 10meV. The nanoscale bridges embedding a two-dimensional electron system are fabricated from AlGaAs/GaAs heterostructures by electron-beam lithography and etching techniques. Narrow constrictions define quantum point contacts that are capacitively controlled via local in-plane side gates. Employing transport spectroscopy, we investigate the transition from electrostatic subbands to Landau-quantization in a perpendicular magnetic field. The large subband quantization energies allow us to utilize a wide magnetic field range and thereby observe a large exchange splitted spin-gap of the two lowest Landau-levels.