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 $\hat{I}”\hat{I}\mu$ of a droplet containing $\sim 30$ electrons created by lateral confinement of a two-dimensional electron gas in GaAs. $\hat{I}”\hat{I}\mu$ becomes very small ($<30\hat{I}¼$eV) near two critical magnetic fields at which the symmetry of the droplet changes and these decreases of $\hat{I}”\hat{I}\mu$ are predicted by Hartree-Fock (HF) for charge excitations. Between the two critical fields, however, the largest measured $\hat{I}”\hat{I}\mu =100\hat{I}¼$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

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