Magnetization measurements of high-mobility two-dimensional electron gases

Abstract

De Haas-van Alphen ͑dHvA͒ oscillations are observed for Landau levels ͑LLs͒ with filling factors between 4 and 52, at temperatures in the range 50 mK to 1 K, in experiments on high-mobility GaAs/͑Al, Ga͒As heterojunctions. The oscillations become sawtooth-shaped at low filling factors, and theoretical fits to the data, assuming the two-dimensional electron gas to be a non-interacting Fermi system, show the shape of LLs to be close to a ␦ function. The small residual width ͑ϳ0.4 meV or less͒ fits equally well to either a Gaussian or a Lorentzian density-of-states model. In almost all cases, a constant background density of states has to be included to obtain a satisfactory fit. Weak odd-filling-factor dHvA peaks are detected at high fields, from which a g-factor enhancement of 15 can be inferred. Comparison of the scattering time derived from the fits before and after illumination, with the momentum relaxation time derived from transport, reveals a counterintuitive behavior in the bulk-modulation-doped sample.

Magnetometry of low-dimensional electron and hole systems

“…However, as we shall discuss shortly, they also performed a quantitative analysis in which they were able to fit the oscillations with a DOS consisting of a sum of a Gaussian, with Γ varying as √ B, and a field-dependent background term. In a similar vein, Zhu et al [71] (using torsionbalance magnetometry on large-area samples) also obtained sawtooth-like dHvA in their two samples (n s = 4.…”

“…The quantity ξ parametrises the fraction of states between LLs. Zhu et al [71] used a full fitting procedure (a development of the method of Potts et al [51]) to reproduce accurately their experimental results, using the broadening Γ and background ξ as the main adjustable parameters. They deduced that either a Lorentzian or a Gaussian DOS would fit the results equally well, with broadening around 0.2 or 0.3 eV, as long as the background term ξ was included.…”

Orbital Magnetism of Graphenes

“…The susceptibility in graphene related systems is expected to be observed by employing the experimental techniques used for two-dimensional electron systems in semiconductor. (66)(67)(68)(69)(70)(71) 7. Acknowledgments…”

De Haas-van Alphen effect and energy gaps of a correlated two-dimensional electron system in an AlAs two-valley pseudospin system

“…A smooth magnetic background has been removed from the raw data by subtracting a low-order polynomial fit in 1 / B. 10,25,26 We find a sawtoothlike dHvA signal whose sharply dropping slopes coincide with the integer filling factors. The peak-to-peak amplitude at filling factor = 2 in panel ͑a͒ amounts to ⌬M =2 = 3.6ϫ 10 −14 J / T, one order of magnitude smaller than in Si/SiGe.…”