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

Potts, A. J. C.; Shepherd, Richard A.; Herrenden-Harker, W G; Elliott, Martin; Jones, C. L.; Usher, A.; Jones, G. A. C.; Ritchie, D. A.; Linfield, E. H.; Grimshaw, Mike

doi:10.1088/0953-8984/8/28/004

Cited by 63 publications

(79 citation statements)

References 26 publications

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“…We checked that in the density range from 3·10 11 cm −2 to 5·10 11ċ m −2 the low-field level broadening is constant (equal to 0.4 meV for sample GaAs-2). The Lorentzian lineshape of the Landau levels is in the agreement with magnetization measurements of Potts et al [28] on the moderate mobility GaAs-based sample. Generally, the shape of DOS in 2D systems is still debated, with a history of research reviewed, e.g., by Usher et al [2].…”

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Temperature derivative of the chemical potential and its magneto-oscillations in a two-dimensional system

et al. 2015

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We report first thermodynamic measurements of the temperature derivative of chemical potential (∂µ/∂T ) in two-dimensional (2D) electron systems. In order to test the technique we have chosen Schottky gated GaAs/AlGaAs heterojunctions and detected experimentally in this 2D system quantum magnetooscillations of ∂µ/∂T . We also present a Lifshits-Kosevitch type theory for the ∂µ/∂T magnetooscillations in 2D systems and compare the theory with experimental data. The magnetic field dependence of the ∂µ/∂T value appears to be sensitive to the density of states shape of Landau levels. The data in low magnetic field domain demonstrate brilliant agreement with theory for non-interacting Fermi gas with Lorentzian Landau level shape.Quantum oscillations are known to be a universal tool to study the electron energy spectrum (Fermi surface cross-sections, electron effective mass and g-factor) in three-dimensional single crystals and two-dimensional (2D) systems. In contrast to the 3D-case, the 2D systems allow in-situ tuning the spectrum and the Fermi energy by various methods (including electric field effect in gated structures, illumination, uniaxial stress etc.), and, hence, allow comprehensive magnetooscillation studies. Quantum oscillations in 2D systems are most often studied in resistivity (Shubnikov-de Haas effect) [ functions µ 1,2 ), the charge of the plates is C(µ 1 − µ 2 )/e, where C is the electric capacitance. Correspondingly, when the two plates are connected electrically and an external parameter varies affecting one of the chemical potential values, a recharging current starts flowing between the plates. The recharging current is proportional to ∆µ (in case the capacitance C varies), ∝ ∂µ/∂n (in case one of the plates is a 2D gas of a density n varying with a gate voltage [6,7]), In our study we apply the technique of measuring ∂µ/∂T similar to that used by Nizhankovskii for bulk samples [10], to the 2D electron systems in magnetic field. We focus on ∂µ/∂T oscillations to compare them with semiclassical theory, and to determine the shape of the density of states of Landau levels. The advantage of the temperature modulation technique is the absence of eddy currents or a background signal (concomitant of many other techniques), and its pure thermodynamic origin.Qualitative discussion. -It is worthwhile to give a qualitative explanation why ∂µ/∂T oscillates with perpendicular magnetic field. For the bare quadratic energy spectrum, ε(p) = p 2 /2m, the single electron density of states is constant in two dimensions. At temperatures T ≪ E F the number of particle-like excitations above µ equals to the number of hole-like excitations below µ (hatched areas in Fig. 1a). Therefore, for a fixed electron density n the chemical potential is independent of temperature, ∂µ/∂T = 0, with exponential accuracy at low temperatures, T ≪ E F , where E F stands for the Fermi energy. In the case of energy dependent density of states (like e.g. in 3D systems, graphene or 2D systems in quantizing magnetic field), one can expand it...

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Temperature derivative of the chemical potential and its magneto-oscillations in a two-dimensional system

et al. 2015

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“…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…”

Section: Resultsmentioning

confidence: 99%

Orbital Magnetism of Graphenes

Koshino¹

2011

Physics and Applications of Graphene - Theory

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“…Smith et al [47,48] modelled magnetocapacitance data using a field-independent Gaussian DOS, but a field-dependent width (Γ ∼ √ B) has also been reported experimentally from dHvA [9] and magnetocapacitance [49] measurements, the latter requiring in addition a constant background DOS. Other experiments though indicate a Lorentzian DOS [50,51]. A more recent theoretical model of Glutsch et al [52] showed that a distorted Gaussian DOS can arise, which depends on LL index.…”

Section: Theory Of the Dhva Effect In 2d Systemsmentioning

confidence: 98%

Magnetometry of low-dimensional electron and hole systems

Usher¹,

Elliott²

2009

J. Phys.: Condens. Matter

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Abstract. The high magnetic field, low-temperature magnetic properties of lowdimensional electron and hole systems reveal a wealth of fundamental information. Quantum oscillations of the thermodynamic equilibrium magnetization yield the total density of states, a central quantity in understanding the quantum Hall effect in 2D systems. The magnetization arising from non-equilibrium circulating currents reveals details, not accessible with traditional measurements, of the vanishingly small longitudinal resistance in the quantum Hall regime. We review how the technique of magnetometry has been applied to these systems, the most important discoveries that have been made, and their theoretical significance.

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

Cited by 63 publications

References 26 publications

Temperature derivative of the chemical potential and its magneto-oscillations in a two-dimensional system

Temperature derivative of the chemical potential and its magneto-oscillations in a two-dimensional system

Orbital Magnetism of Graphenes

Magnetometry of low-dimensional electron and hole systems

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