Polarons in crystalline and non-crystalline materials

Austin, I. G.; Mott, N. F.

doi:10.1080/00018736900101267

Cited by 2,930 publications

(1,288 citation statements)

References 74 publications

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“…As a result they found a frequency-dependent conductivity independent of temperature. Later ͑1969͒, Austin and Mott 23,24 addressed the same approximation, but they considered variable-range hopping between sites, with energy differences of the order of kT or less from the Fermi energy. The equation derived by these authors predicts the slope n in a double-logarithmic plot of conductivity vs frequency to be a decreasing function of frequency.…”

Section: Introductionmentioning

confidence: 99%

Universality of AC conductivity: Random site-energy model with Fermi statistics

2006

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Section: Introductionmentioning

confidence: 99%

Universality of AC conductivity: Random site-energy model with Fermi statistics

2006

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“…In the QMT model, the relaxation time is given by τ ∝ exp(2αR) where α is the decay constant for the s-like wavefunction assumed to describe the localized states and R is the distance separating localized states. The real part of the AC conductivity due to electron tunnelling can be calculated [15,16] using σ (ω) = π 4 384…”

Section: Quantum-mechanical Tunnelling Modelsmentioning

confidence: 99%

“…However, the position of the copper ions is important in that case. Extensive studies have been made of cuprate glasses based on conventional network formers such as P 2 O 5 and B 2 O 3 [3][4][5][6][7]. The high activation energy (about 1 eV) observed in these glasses has been explained assuming a hopping of electrons between non-identical copper sites [5].…”

Section: Introductionmentioning

confidence: 99%

AC conductivity of unconventional bismuth cuprate glass

Hazra¹,

Ghosh²

1997

J. Phys.: Condens. Matter

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Abstract. The frequency dependence of the AC electrical conductivity of different compositions of bismuth cuprate glasses has been presented in the temperature range 80-400 K. The conductivity data have been analysed in terms of different theoretical models to determine the possible conduction mechanism. Analysis of the conductivity data and the frequency exponent shows that the correlated barrier hopping of electrons between Cu + and Cu 2+ ions in the glasses is the most favourable mechanism for AC conduction. The different parameters obtained from the fits of this model to the experimental data are reasonable. The high value of the dielectric constant observed in this glass system can be attributed to the influence of the high polarizability of the Bi 3+ ions of the unconventional network former Bi 2 O 3 on the AC response.

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“…Expanding the energy in a similar way to Eq. (1) but neglecting, so far, the inter-site 10 interaction, we can find that the localized solution has an energy equal to Etrap while the transition state has an energy equal to Etrap/2 making the barrier for the movement of the Jahn-Teller …”

Section: Non-degenerate Two-site Polaron Modelmentioning

confidence: 99%

“…In such a case the polaron behaves like a free electron but with a mass, mp, higher than m* reflecting the electrostatic interaction between the electron and the distorted lattice which can be treated in the continuum approximation 2,[10][11][12][13][14] . A quite different situation holds for small or Holstein polarons 10, 14-15 favored by an increase of m*.…”

Section: Introductionmentioning

confidence: 99%

Stability and Polaronic Motion of Self-Trapped Holes in Silver Halides: Insight through DFT+UCalculations

et al. 2016

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Polarons and their associated transport properties are a field of great current interest both in chemistry and physics. In order to further our understanding of these quasi-particles, we have carried out first-principles calculations of self-trapped holes (STH) in the model compounds AgCl and AgBr, where extensive experimental information exists. Our calculations confirm that the STH solely stabilizes in AgCl but with a binding energy of only 165 meV, an order of magnitude smaller than that found for the Vk center in KCl. Key contributions to this stabilization energy come from the local relaxation along breathing (a1g) and Jahn-Teller (eg) modes in the AgCl6 4-unit. In order to study the transfer of the STH among silver sites we (i) use first-principles calculations to obtain the hopping barrier of the STH to first and second neighbors, involving eight distinct paths, using firstprinciples and (ii) construct a simple model, based on Slater-Koster parameters, that highlights the similarity of polaron transfer with magnetic superexchange. This allows one understanding why the movement of STH to second neighbors is highly enhanced with respect to closer ones. In agreement with experimental data and the model, the present calculations prove the existence of a dominant mechanism of polaronic motion that corresponds to the displacement of the STH to the next nearest sites in the <100> direction and a small barrier of 37 meV. This mechanism is dominated by the covalency inside a AgX6 4-complex (X:Cl;Br) thus explaining why the STH is not stabilized in AgBr following the increase of covalency due to the ClBr substitution. The present calculations confirm that ~10% of the charge associated with the STH in AgCl is lying outside the AgCl6 4-complex. This fact is behind the differences between optical and magnetic properties of the STH in AgCl and those observed in KCl:Ag 2+ .2

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Polarons in crystalline and non-crystalline materials

Cited by 2,930 publications

References 74 publications

Universality of AC conductivity: Random site-energy model with Fermi statistics

Universality of AC conductivity: Random site-energy model with Fermi statistics

AC conductivity of unconventional bismuth cuprate glass

Stability and Polaronic Motion of Self-Trapped Holes in Silver Halides: Insight through DFT+UCalculations

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