Heat capacity of the two-dimensional electron gas in GaAs/AlxGa1−xAs multiple-quantum-well structures

Abstract

We apply the technique of ac calorimetry to a study of the heat capacity of the two-dimensional electron gas (2D EG) in GaAs/${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As multiple-quantum-well structures. Below 2.3 K, we observe the 2D EG contribution to the sample heat capacity, in sweeps of magnetic field B, as oscillations of relative size 0.1%–0.2% periodic in 1/B. The line shape of the oscillations is analyzed with reference to results calculated from theoretical models of the 2D EG density of states (DOS). We find that our experimental line shape is best fitted with a model DOS in which the broadening of the Landau levels oscillates as a function of B. The broadening attains maxima at B such that the heat capacity is at minima. This conclusion is in agreement with recent results from cyclotron-resonance experiments.