Correlation and current anomalies in helical quantum dots

TL;DR

This paper explores the ground-state properties of a topological insulator quantum dot, revealing how spin polarization, quantum phase transitions, Wigner correlations, and persistent currents depend on interaction strength and dot size.

Contribution

It provides a theoretical analysis of electron interactions and topological effects in quantum dots on topological insulator surfaces, highlighting novel quantum phenomena.

Findings

Spin polarization increases with interaction strength.

Quantum phase transitions occur at specific angular momenta.

Persistent current changes sign with dot radius.

Abstract

We theoretically investigate the ground-state properties of a quantum dot defined on the surface of a strong three-dimensional time-reversal invariant topological insulator. Confinement is realized by ferromagnetic barriers and Coulomb interaction is treated numerically for up to seven electrons in the dot. Experimentally relevant intermediate interaction strengths are considered. The topological nature of the dot has interesting consequences: i) spin polarization increases and the ground state exhibits quantum phase transitions at specific angular momenta as a function of interaction strength ii) the onset of Wigner correlations takes place mainly in one spin channel, iii) the ground state is characterized by a persistent current which changes sign as a function of the radius of the dot.