Abstract
The energy spectrum of a two dimensional electron gas in a strong magnetic field consists in the ideal case of discrete Landau levels with a degeneracy corresponding to the number of flux quanta within the area of the sample. The density of states becomes δ-function like and the Landau levels are equally spaced by the cyclotron energy.
The real form of the density of states which is changed by the presence of impurities and potential fluctuations is of great interest for the understanding of all physical phenomena observed in this system.
In this report several different experimental results which are relevant to determine the density of states in a high magnetic field are summarized. Measurements of the specific heat of GaAs/GaAlAs multilayers reveal clear evidence for a Gaussian like density of states super-imposed on a constant background. Temperature dependent measurements of the resistivity in the regime of the Hall plateaus confirms the existence of a flat, mobility dependent background between Landau levels. Magnetization data give evidence of a magnetic field dependence of the Gaussian like density of states and are consistent with significant number of states between Landau levels. Capacitance measurements in the lower magnetic field range are in agreement with the other techniques.
From cyclotron resonance transmission and emission experiments, additional information of the density of states is obtained. The origin of the broadening of the density of states is assigned to impurities in the GaAs in the range of the electron gas and to impurities in the GaAlAs close to the interface. An analysis of cyclotron resonance linewidth at a integer filling factor reveals a systematic dependence of the linewidth on the zero field mobility. The same dependence on mobility proportional to √1/µ is found for the dependence of the amount of flat background states.
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© 1987 Plenum Press, New York
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Gornik, E. (1987). Density of States of 2 Dimensional Systems in High Magnetic Fields. In: Devreese, J.T., Peeters, F.M. (eds) The Physics of the Two-Dimensional Electron Gas. Springer, Boston, MA. https://doi.org/10.1007/978-1-4613-1907-8_11
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DOI: https://doi.org/10.1007/978-1-4613-1907-8_11
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