Long range disorder effects on the heat capacity of two-dimensional electron systems


Broadening of Landau levels of two dimensional electron systems at low temperature and at high perpendicular magnetic fields causes perceptible variations in their interlevel and intralevel excitations as seen in their heat capacity. At a characteristic temperature, the interlevel excitations become negligible and the effect of a small broadening on the energy spectrum vanishes. In this work, a long-range disorder is considered. This can be modeled for the two-dimensional electron gas via a Lorentzian density of states or a Gaussian density of states whose broadening is much larger than kT. The temperature dependence of the heat capacity is derived at half-filled Landau levels or when the chemical potential is a constant. The heat capacity behavior of a system with a long-range disorder is compared to the case of impurity-free quantum Hall systems.