Geometric and impurity effects on quantum rings in magnetic fields

TL;DR

This study examines how impurities and geometric shape influence the magnetic and electronic properties of quantum rings, revealing that magnetic fields and impurities significantly affect Aharonov-Bohm oscillations and magnetic phases.

Contribution

It demonstrates that impurities and geometry alter quantum ring behaviors, and introduces a new computational algorithm for analyzing many-electron systems in magnetic fields.

Findings

Aharonov-Bohm oscillations become insensitive to shape at high magnetic fields and electron numbers.

Impurities can phase-shift or obliterate Aharonov-Bohm oscillations.

A new fourth-order imaginary time projection algorithm accurately computes density matrices in magnetic fields.

Abstract

We investigate the effects of impurities and changing ring geometry on the energetics of quantum rings under different magnetic field strengths. We show that as the magnetic field and/or the electron number are/is increased, both the quasiperiodic Aharonov-Bohm oscillations and various magnetic phases become insensitive to whether the ring is circular or square in shape. This is in qualitative agreement with experiments. However, we also find that the Aharonov-Bohm oscillation can be greatly phase-shifted by only a few impurities and can be completely obliterated by a high level of impurity density. In the many-electron calculations we use a recently developed fourth-order imaginary time projection algorithm that can exactly compute the density matrix of a free-electron in a uniform magnetic field.