Susceptibility of the two-dimensional electron gas: Diamagnetic spikes and gaps in the density of states

In a strong magnetic field, ${\mathrm{Br}}_2$-graphite intercalation compounds behave as nearly ideal two-dimensional (2D) hole gases, with nonoverlapping Landau levels, leading to large diamagnetic spikes in the susceptibility. These spikes are broadened by sample inhomogeneities, corresponding to ∼0.4% density fluctuations. As a byproduct of the analysis, some general features of the 2D susceptibility are clarified.