Few-electron physics in a nanotube quantum dot with spin-orbit coupling

TL;DR

This paper investigates the energy spectrum of few-electron nanotube quantum dots with spin-orbit coupling, revealing how electron interactions and dot length influence ground state transitions and polarization.

Contribution

It provides a detailed analysis of the two-electron phase diagram, highlighting the interplay of spin-orbit coupling, electron interactions, and quantum dot length.

Findings

Ground state transitions are predicted accurately by a single-particle model for short dots.

Critical magnetic field decreases with increasing dot length due to interactions.

Longer dots exhibit spin- and valley-polarized ground states with higher mode occupation.

Abstract

We study the few-electron eigenspectrum of a nanotube quantum dot with spin-orbit coupling. The two-electron phase diagram as a function of the length of the dot and the applied parallel magnetic field shows clear signatures of both spin-orbit coupling and electron-electron interaction. Below a certain critical length, ground state transitions are correctly predicted by a single-particle picture and are mainly independent of the length of the dot despite the presence of strong correlations. However, for longer quantum dots the critical magnetic field strongly decreases with increasing length, which is a pure interaction effect. In fact, the new ground state is spin- and valley-polarized, which implies a strong occupation of higher longitudinal modes.