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

Abstract

The temperature dependence of conductance resonances is used to measure the evolution with the magnetic field of the average level spacing $Δε$ of a droplet containing $\sim 30$ electrons created by lateral confinement of a two-dimensional electron gas in GaAs. $Δε$ becomes very small ($< 30μ$eV) near two critical magnetic fields at which the symmetry of the droplet changes and these decreases of $Δε$ are predicted by Hartree-Fock (HF) for charge excitations. Between the two critical fields, however, the largest measured $Δε= 100μ$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