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...
Far-infrared cyclotron-resonance ͑CR͒ spectroscopy has been used to study a pair of strongly coupled two-dimensional electron gases ͑2DEG's͒ which were formed in two GaAs quantum wells and separated by a thin Al x Ga 1Ϫx As barrier. The degree of wave-function hybridization, along with the effect of a magnetic field parallel to the plane of the electron gas, have been investigated near both the quantum and semiclassical limits, corresponding to low and high filling factors, respectively. Near the quantum regime, the CR transitions in the presence of a small parallel field reveal anticrossing between the Landau levels associated with different hybridized subbands. The energies and intensities of these transitions change with front gate bias, yielding information on the bias dependence of the wave-function hybridization and the subband energy splitting. Close to the semiclassical limit and with strong parallel magnetic fields, two CR peaks are observed. The corresponding cyclotron masses are compared to those expected for noncircular Fermi contours created by anticrossing of the parabolic dispersion curves associated with the coupled 2DEG's. Experimental results in both limits are discussed in the light of predictions from self-consistent solutions of Poisson's and Schroedinger's equations.
We investigate whether quantum history theories can be consistent with Bayesian reasoning and whether such an analysis helps clarify the interpretation of such theories. First, we summarise and extend recent work categorising two different approaches to formalising multi-time measurements in quantum theory. The standard approach consists of describing an ordered series of measurements in terms of history propositions with non-additive 'probabilities'. The non-standard approach consists of defining multi-time measurements to consist of sets of exclusive and exhaustive history propositions and recovering the single-time exclusivity of results when discussing single-time history propositions. We analyse whether such history propositions can be consistent with Bayes' rule. We show that certain class of histories are given a natural Bayesian interpretation, namely the linearly positive histories originally introduced by Goldstein and Page. Thus we argue that this gives a certain amount of interpretational clarity to the non-standard approach. We also attempt a justification of our analysis using Cox's axioms of probability theory.
We attempt a justification of a generalisation of the consistent histories programme using a notion of probability that is valid for all complete sets of history propositions. This consists of introducing Cox's axioms of probability theory and showing that our candidate notion of probability obeys them. We also give a generalisation of Bayes' theorem and comment upon how Bayesianism should be useful for the quantum gravity/cosmology programmes.Comment: 10 pages, accepted by Int. J. Theo. Phys. Feb 200
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.