Magnetic Field Dependence of the Level Spacing of a Small Electron Droplet

TL;DR

This study investigates how the average energy level spacing in a small electron droplet in GaAs varies with magnetic field, revealing deviations from Hartree-Fock predictions and highlighting the role of spin effects.

Contribution

It provides experimental measurements of level spacing evolution with magnetic field, emphasizing the significance of spin degrees of freedom in small electron droplets.

Findings

Level spacing decreases near critical magnetic fields.

Measured level spacing is smaller than Hartree-Fock predictions.

Spin effects are important at certain magnetic fields.

Abstract

The temperature dependence of conductance resonances is used to measure the evolution with the magnetic field of the average level spacing $\Delta\epsilon$ of a droplet containing $\sim 30$ electrons created by lateral confinement of a two-dimensional electron gas in GaAs. $\Delta\epsilon$ becomes very small ($< 30\mu$eV) near two critical magnetic fields at which the symmetry of the droplet changes and these decreases of $\Delta\epsilon$ are predicted by Hartree-Fock (HF) for charge excitations. Between the two critical fields, however, the largest measured $\Delta\epsilon= 100\mu$eV is an order of magnitude smaller than predicted by HF but comparable to the Zeeman splitting at this field, which suggests that the spin degrees of freedom are important. PACS: 73.20.Dx, 73.20.Mf