Discontinuities in the level density of small quantum dots under strong magnetic fields

TL;DR

This study uses exact diagonalization to analyze the level density in a small quantum dot under strong magnetic fields, revealing two distinct regimes related to quasiparticle interactions and non-interacting composite fermions.

Contribution

It provides detailed insights into the level density behavior of small quantum dots under magnetic fields, highlighting the transition between interacting and non-interacting regimes.

Findings

Two regimes in the excitation spectrum: interacting quasiparticles below 0.4 meV and non-interacting composite fermions above 0.4 meV.

Level density increases exponentially at the same rate as the non-interacting model in the higher energy regime.

Discontinuities in level density are observed around the 0.4 meV energy threshold.

Abstract

Exact diagonalization studies of the level density in a six-electron quantum dot under magnetic fields around 7 T (``filling factor'' around 1/2) are reported. In any spin-polarization channel, two regimes are visible in the dot excitation spectrum: one corresponding to interacting quasiparticles (i.e. composite fermions) for excitation energies below 0.4 meV, and a second one for energies above 0.4 meV, in which the level density (exponentially) increases at the same rate as in the non-interacting composite-fermion model.