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  • 1
    Electronic Resource
    Electronic Resource
    Some aspects of electron correlation, magnetism, and localization in spatially disordered systems (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 628-652 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We consider a disordered Hubbard model for a system characterized by quenched liquid-like disorder, with correlation treated at the generalized Hartree–Fock level and the possibility of local magnetic moments introduced from the outset. A simple theory based on averaged Green functions is used to describe the properties of the system in the local moment domains in particular, and their evolution with number density and both structural and electronic parameters of relevance. A probabilistically based mean-field theory is then developed to address the localization characteristics of the HF pseudoparticle states, and the consequent disorder-induced metal–insulator transition. Three principal density domains of interest are identified: a low density insulator with local magnetic moments, a metallic phase with local moments at intermediate densities, and a higher density nonmagnetic metallic state. The theory is used to provide an interpretation of bulk experiments on expanded fluid alkali elements, with particular emphasis on the insulating and "dirty'' metallic domains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460330
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  • 2
    Electronic Resource
    Electronic Resource
    Quantum localization and energy flow in many-dimensional Fermi resonant systems (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 4994-5012 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The quantum mechanics of energy flow in many-dimensional Fermi resonant systems has several connections to the theory of Anderson localization in disordered solids. We argue that in high dimensional and highly quantum mechanical systems the energy flow can be modeled as coherent transport on a locally but weakly correlated random energy surface. This model exhibits a sharp but continuous transition from local to global energy flow characterized by critical exponents. Dephasing smears the transition and an interesting nonmonotonic dependence of energy flow rate on environmental coupling is predicted to occur near the transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458637
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  • 3
    Electronic Resource
    Electronic Resource
    Localizability and dephasing of dipolar excitons in topologically disordered systems (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 7199-7207 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We develop a self-consistent theory for the localizability of dipolar excitations, and the interplay between localization and dephasing mechanisms such as exciton–phonon coupling, within the framework of a tight-binding model of topologically disordered systems. When the dephasing rate vanishes the pure Anderson localization problem may be examined, and we find that dipolar excitations are always extended at any finite density. For sufficiently small number density, however, it is found that while no state in the band is ever strictly localized, the excitation transfer rate is exponentially small, and on the time scale of many experimental probes the excitation would effectively appear to be localized. In the limit of rapid dephasing the present theory correlates with the usual master equation treatments of incoherent (Förster) transport. For sufficiently large disorder, examination of the excitation transfer rate as a function of the dephasing rate predicts a nonmonotonic but continuous crossover from coherent to incoherent transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453363
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  • 4
    Electronic Resource
    Electronic Resource
    Localization versus band crossing transitions in a multiband model of spatially disordered materials (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 6756-6766 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theory is developed to describe the electronic densities of states and localization characteristics of a multiband tight-binding model for a system characterized by quenched liquid-like disorder. For the case of an sp3 system, and with parameters appropriate to fluid mercury at an independent electron level of description, the role of localization is found to be important: localized Fermi-level states persist up to densities considerably higher than that at which the s–p band gap closes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459677
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  • 5
    Electronic Resource
    Electronic Resource
    Mean field theory of a dipolar excitonic insulator transition in matrix-bound systems (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 234-252 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A mean field theory is developed for a dipolar excitonic insulator transition occurring in matrix-bound systems, paradigms of which are low temperature alkali-doped rare gas solids at low impurity concentration. The excitonic insulator transition is driven primarily by changes in the host matrix density, and is a transition from the normal insulating domain in which the impurity electronic ground state is spherically symmetric, to an excitonic phase in which the impurity atoms possess electric dipole moments. A description is given of the electrical and optical characteristics of the system in both the normal insulating phase and the dipolar excitonic state, and it is shown that a variety of properties characteristic of the excitonic state can be deduced from experiment. Comparison is made with experimental results, with which the theory is shown to be compatible, and it is suggested that the dipolar excitonic state may have been observed widely over many years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452614
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  • 6
    Electronic Resource
    Electronic Resource
    Characteristics of GaAs/AlGaAs heterostructures grown by liquid-phase epitaxy on molecular-beam-coated GaAs on Si (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 3201-3204 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Liquid-phase epitaxy has been used to grow four-layer GaAs/AlGaAs double heterostructures on Si substrates that had been precoated with GaAs by molecular-beam epitaxy and coating the remaining exposed parts of the Si wafer with SiO2. Direct growth of GaAs on Si by liquid-phase epitaxy is not feasible because of the dissolution of the Si substrate by the Ga melt. As with the other growth techniques, photoluminescence from the GaAs cap layer and electroluminescence from the 0.2-μm-thick GaAs active layer indicate the luminescence peaks are shifted to lower energy as a result of the tensile strain in the plane of the layers that is caused by the different thermal contraction of the GaAS and Si layers as the wafer is cooled from the growth temperature. Optically pumped stimulated emission is observed from the cap layer at 80 K. The efficiency of the electroluminescence from the active layer was low, indicating the p-n junction was displaced from the active layer due to the accidental excess doping resulting from a slight dissolution of the Si substrate in the Ga melt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341536
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  • 7
    Electronic Resource
    Electronic Resource
    Novel high-pressure isolation cell capable of reaching 120 atm mounted in an ultrahigh-vacuum chamber (1987)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 2292-2294 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A high-pressure cell and manipulator mounted inside an UHV surface analysis chamber has been built which can reach 1800 psi. With this apparatus, catalytic reactions on small surface area (∼1 cm2) single crystals and polycrystalline surfaces are monitored, and the effect of reactant pressure, surface composition, and surface structure are correlated with catalytic activity. This article describes in detail the apparatus and typical experimental procedure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139339
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  • 8
    Electronic Resource
    Electronic Resource
    Anderson localization in topologically disordered systems: The effects of band structure (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 937-948 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A self-consistent theory of localization in a tight-binding model of topologically disordered systems is developed, which explicitly incorporates the influence of irreducible many-body interactions. These interactions are responsible for the detailed band structure of the system and stem from many-body terms in the renormalized perturbation series for the self-energy. The theory employs our previously developed disordered reference system in which the structure of the medium is taken into account, and makes considerable use of statistical mechanical methods which have direct parallels in conventional applications of liquid state theory. The resultant formulation leads to a self-consistent theory for the density of states and the localization characteristics of the system. The central notion of screening is introduced, whereby the simple transfer matrix element is replaced by an energy and density dependent renormalized transfer matrix element. The effect of screening on the mobility edge trajectories is found to be pronounced, and leads to substantially enhanced (diminished) stability of localized state near the upper (lower) band edge in the density of states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451249
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  • 9
    Electronic Resource
    Electronic Resource
    InGaAsP(1.3 μm)/InP vertical-cavity surface-emitting laser grown by metalorganic vapor phase epitaxy (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 889-891 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report InGaAsP/InP vertical-cavity surface-emitting lasers (VCSELs) with an emission wavelength near 1.3 μm grown by metalorganic vapor phase epitaxy. The VCSEL structure contains a double-heterostructure cavity, a metal mirror, and a SiO2/Si dielectric stack (three pairs) mirror with a measured reflectivity of 98%. A threshold current as low as 5 mA for 15-μm-diam devices with a 1-μm-thick active layer at 77 K was achieved, which is close to the best reported value (6 mA) within the accuracy of the pulse measurement. The highest operating temperature was 220 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102619
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  • 10
    Electronic Resource
    Electronic Resource
    High performance InP/InGaAs heterostructure bipolar transistors grown by metalorganic vapor phase epitaxy (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 171-172 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate high performance InGaAs/InP heterostructure bipolar transistors grown by metalorganic vapor phase epitaxy. A unity current gain cutoff frequency fT=78 GHz and a maximum oscillation frequency fmax=42 GHz are achieved in transistors with emitter size 2.5×11 μm2. Ring oscillators using nonthreshold logic show a propagation delay of 31 ps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102133
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