Heat Capacity of the Two-dimensional Electron Gas in GaAs/AlGaAs Multiple Quantum Well Structures.

We apply the technique of ac calorimetry to a study of the heat capacity of the two-dimensional electron gas (2DEG) in GaAs/AlGaAs multiple quantum well structures. Below 2.5K, we observe the 2DEG 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 lineshape of the oscillations is analyzed with reference to results calculated from theoretical models of the 2DEG density of states (DOS). We find that our experimental lineshape 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 recents from cyclotron resonance experiments.