Quantum Interference and Rashba Spin-Orbit Coupling in a Chain of Planar Quantum Rings: Effects on Magnetic and Transport Properties

TL;DR

This study explores how Rashba spin-orbit coupling and magnetic fields influence the magnetic and transport properties of electrons in a chain of quantum rings, revealing complex oscillatory behaviors and phase transitions relevant for spintronics.

Contribution

It demonstrates the impact of Rashba spin-orbit interaction on magnetization and conductance in quantum ring chains, highlighting phenomena like miniband collapse and topological phase effects.

Findings

Rashba coupling causes a transition from diamagnetic to paramagnetic behavior.

Magnetoconductance oscillates with features similar to Shubnikov-De Haas and quantum Hall effects.

Miniband collapse leads to density-of-states oscillations, not quantum Hall mechanisms.

Abstract

Magneto-transport properties of a two-dimensional electron gas in a chain of planar quantum rings are investigated under the Rashba spin-orbit interaction and a transverse homogeneous magnetic field. A modulation potential function models the ring-chain periodicity along one direction and the confinement in the perpendicular one. The electron energy minibands collapse into discrete levels with high degeneracy at specific magnetic field values. The Rashba effect significantly influences the system's properties. Calculations reveal a transition from diamagnetic to paramagnetic behavior in the spin-difference orbital magnetization at high Rashba coupling strengths. This is consistent with the reversal of the spin-difference persistent current observed at the same Rashba values. Total and spin-difference magnetizations exhibit oscillations linked to miniband nodes. The longitudinal magnetoconductance component shows oscillations resembling Shubnikov-De Haas behavior, while the transverse component displays a ladder-like profile reminiscent of the quantum Hall effect. However, both phenomena are more closely associated with the periodic collapse of minibands, leading to strong density-of-states oscillations, rather than with the mechanisms behind the quantum Hall effect. This highlights the rich physics of quantum topological phases in nanostructures with non-trivial geometry. At high Rashba coupling, this behavior degrades. Spin magnetization shows pronounced oscillations, indicating complex interplay between the Zeeman and Rashba effects on spin polarization. These results offer insights into experimentally relevant electronic and spin characteristics attainable in modulated semiconductor structures, contributing to the development of advanced 2D-based materials for magneto-transport and spintronics applications.