Imaging magnetoelectric subbands in ballistic constrictions

TL;DR

This study uses scanning gate experiments to explore magnetoelectric subbands in ballistic constrictions, revealing mode transmission and depopulation transitions influenced by magnetic fields, supported by classical and quantum simulations.

Contribution

It provides the first detailed imaging of magnetoelectric subbands in ballistic constrictions using scanning gate techniques, linking experimental patterns to theoretical models.

Findings

Checkerboard fringe patterns reveal transmitted modes.

Transition from electrostatic to magnetic depopulation observed.

Classical and quantum simulations align with experimental data.

Abstract

We perform scanning gate experiments on ballistic constrictions in the presence of small perpendicular magnetic fields. The constrictions form the entrance and exit of a circular gate-defined ballistic stadium. Close to constrictions we observe sets of regular fringes creating a checker board pattern. Inside the stadium conductance fluctuations governed by chaotic dynamics of electrons are visible. The checker board pattern allows us to determine the number of transmitted modes in the constrictions forming between the tip-induced potential and gate-defined geometry. Spatial investigation of the fringe pattern in a perpendicular magnetic field shows a transition from electrostatic to magnetic depopulation of magnetoelectric subbands. Classical and quantum simulations agree well with different aspects of our observations.