Density of States of Landau Levels from Activated Transport and Capacitance Experiments

Abstract

In this publication we demonstrate that a combination of capacitance measurements with an analysis of thermally activated conductivity seems to be useful for the determination of the density of states (DOS) of Landau levels in two-dimensional systems. The experimental results indicate that no real energy gap exists, but that a nearly energy-independent background density of states (which decreases with increasing electron mobility) is present. Close to the center of the Landau levels the DOS can be described by a Gaussian lineshape with a line width which increases proportional to the square root of the magnetic field. This result agrees with the pre-diction within theself-consistent Born approximation, but the expected variation $\Gamma \sim \sqrt {1/\mu }$ of the line width r with the mobility y of the electrons could not be confirmed.