Interaction-induced magnetization of a two-dimensional electron gas

We consider the contribution of electron-electron interactions to the orbital magnetization of a twodimensional electron gas, focusing on the ballistic limit in the regime of negligible Landau-level spacing. This regime can be described by combining diagrammatic perturbation theory with semiclassical techniques. At sufficiently low temperatures, the interaction-induced magnetization overwhelms the Landau and Pauli contributions. Curiously, the interaction-induced magnetization is third-order in the ~renormalized! Coulomb interaction. We give a simple interpretation of this effect in terms of classical paths using a renormalization argument: a polygon must have at least three sides in order to enclose an area. To leading order in the renormalized interaction, the renormalization argument gives exactly the same result as the full treatment.