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  • 1
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    Determining a hopping polaron's bandwidth from its Seebeck coefficient: Measuring the disorder energy of a non-crystalline semiconductor (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-01-26
    Description: Charge carriers that execute multi-phonon hopping generally interact strongly enough with phonons to form polarons. A polaron's sluggish motion is linked to slowly shifting atomic displacements that severely reduce the intrinsic width of its transport band. Here a means to estimate hopping polarons' bandwidths from Seebeck-coefficient measurements is described. The magnitudes of semiconductors' Seebeck coefficients are usually quite large (〉 k/ | q | = 86  μ V/K) near room temperature. However, in accord with the third law of thermodynamics, Seebeck coefficients must vanish at absolute zero. Here, the transition of the Seebeck coefficient of hopping polarons to its low-temperature regime is investigated. The temperature and sharpness of this transition depend on the concentration of carriers and on the width of their transport band. This feature provides a means of estimating the width of a polaron's transport band. Since the intrinsic broadening of polaron bands is very small, less than the characteristic phonon energy, the net widths of polaron transport bands in disordered semiconductors approach the energetic disorder experienced by their hopping carriers, their disorder energy.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Anisotropic small-polaron hopping in W:BiVO4 single crystals (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-01-13
    Description: DC electrical conductivity, Seebeck and Hall coefficients are measured between 300 and 450 K on single crystals of monoclinic bismuth vanadate that are doped n -type with 0.3% tungsten donors (W:BiVO 4 ). Strongly activated small-polaron hopping is implied by the activation energies of the Arrhenius conductivities (about 300 meV) greatly exceeding the energies characterizing the falls of the Seebeck coefficients' magnitudes with increasing temperature (about 50 meV). Small-polaron hopping is further evidenced by the measured Hall mobility in the ab -plane (10 −1  cm 2  V −1  s −1 at 300 K) being larger and much less strongly activated than the deduced drift mobility (about 5 × 10 −5  cm 2  V −1  s −1 at 300 K). The conductivity and n -type Seebeck coefficient is found to be anisotropic with the conductivity larger and the Seebeck coefficient's magnitude smaller and less temperature dependent for motion within the ab -plane than that in the c -direction. These anisotropies are addressed by considering highly anisotropic next-nearest-neighbor (≈5 Å) transfers in addition to the somewhat shorter (≈4 Å), nearly isotropic nearest-neighbor transfers.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 3
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    High-density Two-Dimensional Small Polaron Gas in a Delta-Doped Mott Insulator (2013)
    Springer Nature
    Details
    Publication Date: 2013-11-22
    Description: Heterointerfaces in complex oxide systems open new arenas in which to test models of strongly correlated material, explore the role of dimensionality in metal-insulator-transitions (MITs) and small polaron formation. Close to the quantum critical point Mott MITs depend on band filling controlled by random disordered substitutional doping. Delta-doped Mott insulators are potentially free of random disorder and introduce a new arena in which to explore the effect of electron correlations and dimensionality. Epitaxial films of the prototypical Mott insulator GdTiO3 are delta-doped by substituting a single (GdO)+1 plane with a monolayer of charge neutral SrO to produce a two-dimensional system with high planar doping density. Unlike metallic SrTiO3 quantum wells in GdTiO3 the single SrO delta-doped layer exhibits thermally activated DC and optical conductivity that agree in a quantitative manner with predictions of small polaron transport but with an extremely high two-dimensional density of polarons, ~7 × 1014 cm−2. Scientific Reports 3 doi: 10.1038/srep03284
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
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  • 4
    Electronic Resource
    Electronic Resource
    Ab initio self−consistent field (SCF) calculations on borane icosahedra with zero, one, or two substituted carbon atoms (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6815-6822 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Restricted Hartree–Fock calculations at the double-zeta level are performed for the closed-shell isoelectronic molecules B12H−212, CB11H−12 , and 1,12-C2 B10 H12 . The geometries are optimized and the vibrational spectra are obtained. The behavior of the molecular orbitals upon carbon substitution is analyzed. The results are compared with the available experimental and theoretical results from the literature. The main features of the electronic structure are correctly described at this level of approximation. The new results can aid in the interpretation of photoemission, infrared absorption, and Raman scattering experiments on these molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455355
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  • 5
    Electronic Resource
    Electronic Resource
    Peltier heat of a small polaron in a magnetic semiconductor (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3213-3215 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For the first time the heat transported with a small polaron in both antiferromagnetic and ferromagnetic semiconductors is calculated. This heat, the Peltier heat, π, is obtained from the change of the entropy of the total system upon introduction of a charge carrier. We explicitly consider both the intrasite and intersite exchange interactions between a small polaron and the interacting spins of a spin-1/2 magnet. There are two competing magnetic contributions to the Peltier heat. First, adding the carrier increases the spin entropy of the system. This provides a positive contribution to π. Second, the exchange between the carrier and the sites about it enhances the exchange binding between these sites. This reduces the energetically allowable spin configurations and provides a negative contribution to π. At extremely high temperatures when kT exceeds the intrasite exchange energy, the first effect dominates. Then π is simply augmented by kT ln 2. However, well below the magnetic transition temperature the second effect dominates. In the experimentally accessible range between these limits both effects are comparable and sizable. The net magnetic contribution to the Peltier heat rises with temperature. Thus, a carrier's interactions with its magnetic environment produces a significant and distinctive contribution to its Peltier heat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335154
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  • 6
    Electronic Resource
    Electronic Resource
    Large bipolarons and superconductivity (1995)
    Springer
    Journal of superconductivity 8 (1995), S. 523-526 
    Details
    ISSN: 1572-9605
    Keywords: Bipolarons ; infra-red absorption ; mobility ; liquid ; superconductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Superconductivity has long been speculated to result from charge carriers paired as mobile charged bosons. Although the pairing of carriers as small (single-site) bipolarons is known, small bipolarons readily localize. By contrast, large (multi-site) bipolarons, in analogy with large polarons, should be mobile. It is shown that large bipolarons can form in solids with very displaceable ions, e.g., many oxides. Large-polaronic (but not small-polaronic) carriers produce absorption spectra like the carrier-induced absorptions observed in cuprates. Redistribution of the self-trapped carriers of large bipolarons among sites of carriers' molecular orbitals in response to atomic motions lowers phonon frequencies. The dependence of the phonon zero-point energy on the spatial distribution of large bipolarons produces a phonon-mediated attraction between them. This dynamic quantum-mechanical attraction fosters the condensation of large bipolarons into a liquid. Superconductivity can result when the large-bipolarons' groundstate remains liquid rather than solidifying.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00722846
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  • 7
    Electronic Resource
    Electronic Resource
    Explicit studies of the quantum theory of light interstitial diffusion (1979)
    Springer
    Hyperfine interactions 6 (1979), S. 255-259 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01028803
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  • 8
    Electronic Resource
    Electronic Resource
    The positive muon as a small polaron (1981)
    Springer
    Hyperfine interactions 8 (1981), S. 515-523 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A positive muon in a solid is typically taken to selftrap and move in analogy with an electronic small polaron. Here the dynamics of self-trapping and small-polaron motion are described. It is stressed that the physical circumstances defining electronic and light-interstitial small-polaron formation and motion differ qualitatively from one another. The muon is an intermediate case which in some instances is a unique hybrid of these two situations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01037521
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  • 9
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    Small-Polaronic Diffusion of Light Interstitials in bcc Metals (1979)
    American Physical Society
    Details
    Publication Date: 1979-03-19
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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  • 10
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    Formation, motion, and high-temperature superconductivity of large bipolarons (1989)
    American Physical Society
    Details
    Publication Date: 1989-03-27
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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