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  • 1
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    Demographic history and rare allele sharing among human populations (2011)
    National Academy of Sciences
    Details
    Publication Date: 2011-07-05
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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    PAPER CURRENT
  • 2
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    Rock magnetic identification and geochemical process models of greigite formation in Quaternary marine sediments from the Gulf of Mexico (IODP Hole U1319A) (2008)
    In:  EPIC3Earth and Planetary Science Letters, 275, pp. 233-245
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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    PAPER (OA)
  • 3
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    Subduction Reversal in a Divergent Double Subduction Zone Drives the Exhumation of Southern Qiangtang Blueschist‐Bearing Mélange, Central Tibet (2021)
    Details
    Publication Date: 2021-07-01
    Description: (Ultra) high‐pressure (HP) rocks can be exhumed rapidly by subduction reversal or divergent plate motion. Recent studies show that subduction reversal can in particular occur in a divergent double subduction zone when the slab pull of one slab exceeds that of the other, shorter one, which then experiences a net upward pull. This recent hypothesis, first proposed for Triassic HP‐rocks exposed in the central Qiangtang mélange belt in central Tibet, can explain the exhumation of (ultra) HP rocks through upward slab movement. However, this model lacks the support of kinematic evidence. In this study, based on the recognition of multiple deformational phases, we analyze the kinematics of the HP‐bearing mélange in central Qiangtang. Based on new 40Ar‐39Ar geochronology data and those collected from the literature, we present a temporal framework for the new observations. We recognize a switch in sense of shear between the prograde (D1) and exhumation (D2‐3) paths. The change of shear sense reflects the reversal from downward to upward movement of the oceanic slab below. Early D2 represents the early exhumation stage that caused retrograde metamorphism from eclogite to blueschist facies. No magmatism occurred during this period. Continued exhumation from blueschist facies to greenschist facies resulted in D2‐D3 structures. Voluminous igneous activity occurred during this stage. We suggest that subduction reversal in a divergent double subduction zone can best explain the kinematic evolution and temporal framework above. This exhumation model may provide a new perspective on the exhumation mechanism for other HP rocks around the world.
    Description: Key Points: Central Qiangtang HP‐bearing mélange formed by short‐lived southward subduction in a divergent double subduction setting. Progressive inversed shearing exhumed HP rocks. Subduction reversal in a divergent double subduction zone can exhume HP rocks through direct slab movement.
    Description: China Geological Survey (CGS) http://dx.doi.org/10.13039/501100004613
    Keywords: 551.8 ; Tibetan Plateau ; South Qiangtang Terrane ; subduction reversal ; divergent double subduction zone ; exhumation ; high‐pressure rocks
    Type: article
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    CITATION GEO-LEO
  • 4
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    Time constraints, magnetic mineralogy and geochemistry for overpressured sediments from the continental slope in the northwestern Gulf of Mexico (2007)
    In:  EPIC3EGU 2007, Vienna, Austria, 2007-04-2007
    Details
    Publication Date: 2015-03-04
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 5
    Electronic Resource
    Electronic Resource
    Valence band structures of heavily doped strained GexSi1−x layers (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 402-407 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Valence-band structure and density-of-state (DOS) effective mass are calculated for heavily p-type-doped Si and strained GexSi1−x layers grown on (100) Si. At low doping values calculations have been made by earlier authors and the results agree with the published values of DOS mass by these authors. The Fermi energy EF measured from the valence-band edge has been calculated using our values of DOS effective mass. At 1020 cm−3 doping level the value is 77.3 meV compared with 80 meV determined from luminescence experiments. The value of EF obtained by using the normally accepted value of 0.57 for the hole effective mass in Si is more than the experimental value by a factor about 2, i.e., the calculations reduce the discrepancy from 100% to less than 4%. The effective barrier height of (p+-Ge0.42Si0.58)/(p-Si) internal photoemission photo detector has also been calculated using our calculated value of the DOS hole mass. The calculated value is in reasonable agreement with the experimental value. The values of the band parameters and of deformation potentials are known only for small values of k and energies. These values have been used at large doping concentrations where k and energy are also large. The agreement of the theory with experiment suggests that the values of the parameters are valid approximately at higher energies also.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354123
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  • 6
    Electronic Resource
    Electronic Resource
    Response of a semiconductor tunneling structure to a time-dependent perturbation (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 3593-3597 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The one-dimensional electron resonant tunneling spectrum (I-V characteristics) is calculated for a GaAs/AlGaAs double barrier resonant tunneling structure in the presence of a small time-dependent electric field, assuming a coherent tunneling mechanism and local equilibrium in the electrodes. The small time-dependent signal is applied as a probe perturbation in addition to the usual dc voltage. When the perturbation frequency is 4.6×1012 rad/s, the calculated current density at resonance is maximally decreased in response to the external ac perturbation. The current density returns to its dc value when the perturbation frequency is higher than ωmax=1.5×1013 rad/s. It is interpreted that the response time for the tunneling electrons in this structure is of the order of τ=1/ωmax=6.7×10−14 s. The comparison of this calculation result with the experiment [τ=6.5×10−14 s, T. C. L. G. Sollner, E. R. Brown, W. D. Goodhue, and H. Q. Le, Physics of Quantum Electron Devices, edited by F. Capasso (Springer, Berlin, 1990), p. 147] suggests that the speed of the electron redistribution in the time-dependent wave functions is very fast in these tunneling structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352298
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  • 7
    Electronic Resource
    Electronic Resource
    Resonant tunneling of holes in Si/GexSi1−x (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 7468-7473 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The compressional strain in GexSi1−x grown on Si moves the light-hole (LH) band down and the heavy-hole (HH) band up, while the tensile strain in Si grown on GexSi1−x moves the LH band up and the HH band down. In the tunneling structure of Si/GexSi1−x grown on a Si substrate with a GexSi1−x or Si buffer layer, the band offsets of LH and HH are then changed depending on the strain in Si/GexSi1−x, which is influenced by the lattice relaxation of the buffer layer. In this work the Fermi level Ef of the tunneling structure is investigated from the energy band structure calculations to provide information for tunneling current calculations and peak identification in comparison with experimental I-V spectra. When a Si buffer layer is used, only the HH band of the GexSi1−x spacer is found to be filled so that the tunneling current is HH characteristic. With a GexSi1−x buffer layer both LH and HH contribute to the total tunneling current. The effective mass approximation is also investigated for Si/GexSi1−x tunneling structures and a quasiparticle (HH, LH, and the spin-orbital splitoff) tunneling picture is justified for theoretical analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349742
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  • 8
    Electronic Resource
    Electronic Resource
    The interaction between electron and phonon localized in a double-barrier resonant tunneling diode (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3264-3269 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electron-phonon interaction (the transition probability from the initial electronic state to the final state via the electron-phonon interaction) is analyzed when electrons and phonons are either extended or localized in a quantum system. Compared with the situation of the bulk material where all wave functions are extended, it is generally found that the electron-phonon interaction is reduced when one state is localized while it will be enhanced when more states involved in the interaction process become localized. It has been shown that the electron-phonon interaction is inversely proportional to the well width when all the states involved are localized. Special attention is then focused on the double-barrier resonant tunneling diode. A simple Monte Carlo scheme is developed to include the electron-phonon interaction process in the quantum well between two barriers. The numerically calculated I-V characteristics agrees much better with the experimental spectra if the electron-phonon interaction has been taken into account.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354546
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  • 9
    Electronic Resource
    Electronic Resource
    Charge accumulation and band edge in the double barrier tunneling structure (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 3877-3882 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Due to various scattering processes, the wave function coherence is broken during transport in the double barrier resonant tunneling structure (DBRTS). Based on this coherence breakdown, local states are assumed to exist in the well region in DBRTS and the Schrödinger equation is solved self-consistently together with the Poisson equation. The properties of the charge accumulation in local states are investigated and presented as possible mechanisms to explain three sets of recent experimental results: (a) the redshift and broadening of photoluminescence and photoluminescence excitation peaks, (b) the peak in the specific capacitance-voltage spectrum at the resonance, and (c) the appearance/disappearance of the shoulder peak adjacent to the resonance peak in I-V spectra without/with an external capacitor connected in parallel to the DBRTS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350853
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of impurity and phonon scattering effects in resonant tunneling structures (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1874-1878 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tunneling properties and their temperature variations of molecular bean epitaxy grown symmetric AlAs/GaAs/AlAs resonant tunneling diodes with thin barriers are studied theoretically and experimentally. The measured peak and valley current densities show strong dependences on temperature. A Monte Carlo simulation including impurity and optical-phonon scatterings is developed for the calculation of the current-voltage behavior of the double barrier structures. This approach reveals pronounced temperature dependent tunneling features which agree well with measured results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354795
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