Magnetization studies of Landau level broadening in two-dimensional electron system

We have used a torque magnetometer to measure de Haas-van Alphen oscillations in the magnetization of two-dimensional electrons in GaAs/AlGaAs heterostructures and multiple quantum well systems for temperatures ranging from 0.125 K to 4.2 K and in magnetic fields of up to 15 T. Our results indicate that for high magnetic fields the density of states can be described by a series of Lorentzian broadened Landau levels with a broadening that is independent of the magnetic field, B, and Landau level index, n. However, at low magnetic fields the Lorentzian broadened density of states becomes indistinguishable from a Gaussian one with a broadening that is proportional to B½. The high field behaviour of the Landau level line-shape is shown to differ appreciably from the low field case as reported by other workers using both magnetization and other experimental methods. The reliability of this and other experimental techniques is discussed