Specific Heat of Two-Dimensional Electrons in GaAs-GaAlAs Multilayers

Gornik, E.; Lassnig, R.; Strasser, G.; Störmer, H. L.; Gossard, A. C.; Wiegmann, W.

doi:10.1103/physrevlett.54.1820

Cited by 253 publications

(123 citation statements)

References 8 publications

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“…This is in contradiction to experimental results [1][2][3][4][5][6][7][8]. To compare with experiment we shall employ a recent statistical model of inhomogeneities in the electron density n, [9] , which has been found to explain well the results of the earlier mentioned indirect measurements of the DOS [1][2][3][4][5][6][7][8][9]11]. …”

Section: -E(-~)~e-~d T "Drcontrasting

confidence: 47%

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Magnetic field dependence of gate voltage and current in a GaAs-heterostructure in the quantum hall regime

Weiss¹,

Mosser²,

Guðmundsson³

et al. 1987

Solid State Communications

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The current flow at a fixed gate voltage and the floating gate voltage for fixed charge density in a gated GaAs heterostructure have been measured as a function of the magnetic field. The voltage oscillations which reflect the behaviour of the chemical potential have been clearly resolved. The experimental results are explained by a statistical model of inhomogeneities in the carrier concentration implying an effective density of states between the Landau levels.Recently, measurements have been performed on GaAs-heterostructures in order to obtain information about the density of states (DOS) of a twodimensional electron gas (2DEG) in a strong quantizing magnetic field. The activation energy of P~z [1][2][3], the capacitance [4][5][6], the specific heat [7] and the magnetization [8] have been investigated. Some of these measurements are sensitive only in certain energy regions of the DOS. The capacitance measurement fails [4,5] for example in the interesting region between the Landau levels due to the vanishing conductivity of the 2DEG in that region. This problem of high series resistance can be reduced by using a backside contact (n +) instead of the channel contacts [6]. In the present paper we will discuss another type of measurement which is closely related to the capacitance measurement but more sensitive to the actual form of the DOS in the whole magnetic field region, even though channel contacts are used. In this measurement the current between the top gate and the 2DEG is measured as a function of the magnetic field B. This current, the " gate current", is directly related to the changes in the DOS and the capacitance as a function of B [2,9]. We also report a measurement of the gate voltage Vg, i.e. the voltage between the gate and the 2DEG, as a function of B. In comparision to earlier experiments [t0] we see clear oscillations which follow quantitatively the variation of the chemical potential # of the 2DEG. The results from the gate current measurement [2] can only be explained poorly by the adhoc simple background model assuming a constant background. On the other hand a recently proposed model [9,11] on statistical inhomogeneities of the carrier density no is shown to reproduce the experimental results excellently, both in the case of the gate current and the gate voltage. After a description of the experimental set up the inhomogeneity model will briefly be introduced. Then the experimental results will be discussed and compared with calculations based on the inhomogeneity model.The experiments described here have been carried out on an A1GaAs-GaAs heterostructure with a low temperature mobility/~ = 585, O00cm2/V8 and a carrier density n, = 1.90 • 1011cm-2. The sample has the usual mesa Hall geometry (see Fig. 1) with an Au-gate on top (area 5.65mm2). All potential probes were short circuited and acted as a channel contact. The top layers (GaAs/Si-doped A1GaAs and undoped A1GaAs spacer) are completely depleted and therefore insulating. Both, current (gate voltage V 9 = const) and voltage (carrie...

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Section: -E(-~)~e-~d T "Drcontrasting

confidence: 47%

“…The activation energy of P~z [1][2][3], the capacitance [4][5][6], the specific heat [7] and the magnetization [8] have been investigated. Some of these measurements are sensitive only in certain energy regions of the DOS.…”

mentioning

confidence: 99%

Magnetic field dependence of gate voltage and current in a GaAs-heterostructure in the quantum hall regime

Weiss¹,

Mosser²,

Guðmundsson³

et al. 1987

Solid State Communications

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“…al., 1986). In a homogeneous 2-DEG it has been shown experimentally that the LL linewidth T has a magnetic field dependence of the form T oc B a with 0 < a < 0.5 (Weiss and von Klitzing, 1987;Gornik et al, 1985;Eisenstein et al, 1985), whereas theoretically T oc \J~B is expected for short range scatterers and T independent of B for long range scatterers (Ando and Uemura, 1974;Gerhardts, 1975). Since the Landau level degeneracy is proportional to B, the peak values of the DOS in the individual LL's and, as a consequence, the peak values of the capacitance are expected to increase monotonically with a structureless envelope with increasing magnetic field.…”

Section: In a 2-deg C(b) Oscillates As A Function Of The Magnetic Fimentioning

confidence: 99%

Magnetoquantum Oscillations in a Lateral Superlattice

Weiss

1990

Electronic Properties of Multilayers and Low-Dimensional Semiconductor Structures

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The low temperature magnetoresistance of a high mobility two-dimensional electron gas is dominated by Shubnikov-de Haas oscillations, reflecting the discrete nature of the electron energy spectrum. When a weak one-or two-dimensional periodic potential is superimposed on the two-dimensional electron gas a novel type of oscillations occurs which reflects the commensurability of the relevant lengths in these systems -the cyclotron orbit diameter at the Fermi energy and the period a of the periodic potential. In addition the electron mean free path le also plays a role since the effect is observable only in mesoscopic systems where le is significantly longer than the period a of the potential. The essential aspects of these novel commensurability oscillations are discussed here in detail, starting from the discussion of same basic magnetotransport properties in an unmodulated two-dimensional electron gas (2-DEG). INTRODUCTION: MAGNETOTRANSPORT IN A 2-DEG

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“…On the other hand, the equilibrium properties (say specific heat) of the system depend simply on the density of states [5,6]. These properties cannot distinguish the localized states from extended states.…”

mentioning

confidence: 99%

“…Agreeably, the separation of electronic specific heat from lattice specific heat in quantum Hall systems, from the experimental data, are extremely difficult. However, the experiments [5,7] are performed in multilayer systems to extract electronic specific heat.…”

mentioning

confidence: 99%

Specific heat in the integer quantum Hall effect: An exact diagonalization approach

Mandal

Acharyya

1998

Physica B: Condensed Matter

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We have studied the integer quantum Hall effect at finite temperatures by diagonalizing a single body tight binding model Hamiltonian including Aharonov-Bohm phase. We have studied the energy dependence of the specific heat and the Hall conductivity at a given temperature. The specific heat shows a sharp peak between two consecutive Hall plateaus. At very low temperatures, the numerical results of the temperature variations of specific heat (in the plateau region) are in good agreement with the analytical results. PACS number(s): 73.40. Hm, 71.30.+h

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Specific Heat of Two-Dimensional Electrons in GaAs-GaAlAs Multilayers

Cited by 253 publications

References 8 publications

Magnetic field dependence of gate voltage and current in a GaAs-heterostructure in the quantum hall regime

Magnetic field dependence of gate voltage and current in a GaAs-heterostructure in the quantum hall regime

Magnetoquantum Oscillations in a Lateral Superlattice

Specific heat in the integer quantum Hall effect: An exact diagonalization approach

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