Cyclotron-resonance studies of strongly coupled double quantum wells in tilted magnetic fields near the quantum and semiclassical limits

Arnone, D. D.; Marlow, Thomas; Foden, C. L.; Linfield, Edmund H.; Ritchie, D. A.; Pepper, M.

doi:10.1103/physrevb.56.r4340

Cited by 21 publications

(18 citation statements)

References 6 publications

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“…However, subsequent reinterpretation of these experimental results by other investigators [8,9] has suggested hybridized electron and hole Landau levels as a possible description. FIR CR spectroscopy is ideally suited to elucidate the nature of this ground state because it is a sensitive probe of the internal modes (e.g., 1s to 2p) of excitons [10] as well as wave function hybridization [11].In the present study, FIR CR spectroscopy is used to investigate the ground state of both strongly ͑D 1.75 meV͒ and weakly hybridized ͑D , 0.3 meV͒ electron-hole gases in InAs͞GaSb quantum wells. The latter is realized by insertion of a 15 Å AlSb barrier between the InAs and GaSb wells.…”

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“…Strong hybridization was realized in a 150 Å InAs͞100 Å GaSb structure, where the hybridization gap D 1.75 meV was determined from the temperature dependence of the resistance versus N e and N h , using the method in Ref. [11]. By contrast, weak hybridization was achieved in a 150 Å InAs͞15 Å AlSb͞150 Å GaSb structure, where the AlSb barrier had the effect of significantly reducing the hybridization occurring between electron and hole states, yielding a calculated estimate of D , 0.3 meV [13].…”

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Ground State of a Two-Dimensional Coupled Electron-Hole Gas inInAs/GaSbNarrow Gap Heterostructures

et al. 1999

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The contributions of wave function hybridization and spontaneous exciton formation to the ground state of closely spaced electron and hole gases in InAs͞GaSb heterostructures were investigated using cyclotron resonance (CR) spectroscopy. Strongly hybridized samples exhibit two electronlike CR absorptions at all perpendicular magnetic fields. The high frequency mode neither disappears at high temperatures ͑ϳ100 K͒ nor is affected by changes in electron or hole density, but is eliminated by a high parallel magnetic field ͑ϳ7 T͒. These effects can be understood as signatures of electron-hole wave function hybridization, and cannot be explained in terms of an excitonic gas.[S0031-9007(99)08733-5] PACS numbers: 73.20.Dx, 73.40.Kp, 78.66.Fd The formation of a thermodynamically stable excitonic ground state in a narrow gap semiconductor is a possible precursor to Bose-Einstein condensation in such systems. In order to achieve this, the band gap energy E g of the semiconductor must be smaller than the exciton binding energy E b , making it energetically favorable to spontaneously form excitons. To achieve E g , E b , InAs͞GaSb heterostructures have been proposed [1-3] because the gap between the InAs conduction band and the GaSb valence band can be tuned from ϳ 2150 meV to positive values [4]. Thus, the spontaneous formation of an excitonic gas might be realized using closely spaced InAs and GaSb quantum wells, containing two-dimensional electron and hole states, respectively. To achieve the large E b needed for experimental observation of such excitons, the distance between the gases should be minimized, maximizing the Coulombic attraction between the electrons and holes. Whether such an excitonic gas forms the ground state of the system depends on other competing mechanisms. In particular, as the interwell separation decreases, conduction and valence band wave function overlap results in hybridized states characterized by a new band gap energy D [4]. Additional considerations such as high and unequal extrinsic populations of electrons and holes may also inhibit exciton formation. Recent far-infrared (FIR) cyclotron resonance (CR) studies [5,6] of adjacent electron-hole gases in InAs͞Al x Ga 12x Sb heterostructures revealed two absorption peaks near the electron CR energy at x 0.1 and 0.2. These were not attributable to two occupied electron subbands as in early CR studies of InAs͞GaSb multiheterojunctions [7]. Instead, the lower energy peak was assigned to electron CR, and the higher energy peak to a cyclotron-shifted internal transition of a ground excitonic state. However, subsequent reinterpretation of these experimental results by other investigators [8,9] has suggested hybridized electron and hole Landau levels as a possible description. FIR CR spectroscopy is ideally suited to elucidate the nature of this ground state because it is a sensitive probe of the internal modes (e.g., 1s to 2p) of excitons [10] as well as wave function hybridization [11].In the present study, FIR CR spectroscopy is used to investigat...

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Ground State of a Two-Dimensional Coupled Electron-Hole Gas inInAs/GaSbNarrow Gap Heterostructures

et al. 1999

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“…The effects related to the intersection of different Landau levels belonging to different subbands were studied both theoretically and experimentally for double quantum well structures. 8 Unlike the double-well case the intersection of levels in the two-subband single heterojunction occurs at much higher magnetic field, which makes all field-dependent many-body effects more pronounced.…”

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Two-subband system in quantizing magnetic field: probing many-body gap by non-equilibrium phonons

Apalkov

Portnoi

2002

Physica E: Low-dimensional Systems and Nanostructures

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We study the many-body effects in a two-subband quasi-two-dimensional electron system in a quantizing magnetic field at filling factor three. A manifestation of these effects in the phonon absorption spectroscopy is discussed. The electron system is mapped onto a two-level system with the separation between levels determined by the intersubband splitting and the cyclotron energy. The electron-electron interaction enhances the excitation gap, which exists at all values of the interlevel splitting. This results in a single-peak structure of the phonon absorption rate as a function of magnetic field, instead of the double-peak structure for non-interacting electrons.

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“…The photoluminescence line shape depends on the modification of hole states and is due to the many-particle interaction. 12 In the recent years, a weak perpendicular magnetic field has been employed as a probe in order to study the effects of in-plane field on tunnel-coupled states of electrons ͑Shubnikov-de Haas oscillations 5 and cyclotron resonance absorption 13 have been measured͒. Note that all aforementioned papers deal with the transport properties when the peculiarities of the energy spectra together with other factors ͑scattering processes, transformation of the hole states͒ are essentials.…”

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Level anticrossing effect on electron properties of coupled quantum wells under an in-plane magnetic field

1999

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The influence of an in-plane magnetic field on the energy spectrum and zero-temperature equilibrium properties of tunnel-coupled double and triple quantum wells is studied. Both the appearance of the gap due to anticrossing of two energy branches and the peculiarities of the third-order crossing point ͑for symmetric triple quantum well case͒ are discussed. As results, magnetization of two-dimensional electrons in double and triple quantum wells is modified essentially if the Fermi level is localized near such peculiarities. Another effect under consideration is the interlevel charge redistribution between quantum wells and the transverse voltage induced by the in-plane magnetic field. Self-consistent numerical calculations for double and triple quantum wells, which take into account the modifications of energy spectra under gate voltage, are presented.

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Cyclotron-resonance studies of strongly coupled double quantum wells in tilted magnetic fields near the quantum and semiclassical limits

Cited by 21 publications

References 6 publications

Ground State of a Two-Dimensional Coupled Electron-Hole Gas inInAs/GaSbNarrow Gap Heterostructures

Ground State of a Two-Dimensional Coupled Electron-Hole Gas inInAs/GaSbNarrow Gap Heterostructures

Two-subband system in quantizing magnetic field: probing many-body gap by non-equilibrium phonons

Level anticrossing effect on electron properties of coupled quantum wells under an in-plane magnetic field

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