Quasiparticle Theory of Defects in Solids

Pushkarov, D. I.

doi:10.1142/1071

Cited by 19 publications

(35 citation statements)

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“…If the temperature is small enough (the exact conditions will be derived below) the number of phonons is negligible, and the defecton free path is controlled by defecton-defecton interaction. Defecton-defecton scattering possesses a series of peculiarities relevant to the energy band width [1,18,19,2]. First of all, the quasiparticle energy cannot vary during the motion more than the energy band width ∆.…”

Section: Defecton-defecton Scatteringmentioning

confidence: 99%

“…The quantity σ for the potential (16) with n = 3 in quasiclassical approximation is of the form [30,2] …”

Section: Defecton-defecton Scatteringmentioning

confidence: 99%

“…As it has been shown by I.M. Lifshitz [34] (see also [35,36]) such a problem can be solved in an analytical form [1,2,3]. The differential cross-section for the scattering of a phonon of the j-th mode with polarization ν as a result of which a phonon of the i-th mode with a polarization ν is produced is given by the expression [1]: …”

Section: Phonon Controlled Diffusionmentioning

confidence: 99%

“…The spectrum is given by the defecton dispersion law (k). In a tight binding approximation it has the form (k) = Φ + Aω(k) ( 2 ) where Φ is the activation energy of a localized defect, A is the tunnelling probability amplitude (exchange integral), and ω(k) is a dimensionless function which depends on the symmetry of the crystal lattice. For a simple cubic lattice the dispersion law is of the form (k) = Φ + A(cos k x a + cos k y a + cos k z a)…”

Section: Introductionmentioning

confidence: 99%

“…by means of nuclear magnetic resonance (NMR) [10]. [2,11]. The degeneracy temperature T 0 is extremely small:…”

Section: Introductionmentioning

confidence: 99%

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Quantum diffusion

Pushkarov

2004

Open Physics

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Basic ideas and results which characterize quantum diffusion of defects in quantum crystals like solid helium as a new phenomenon are presented. Quantum effects in such media lead to a delocalization of point defects (vacancies, impurities etc.) and they turn into quasiparticles of a new type -defectons, which are characterized not by their position in the crystal lattice but by their quasimomentum and dispersion law. Defectondefecton and defecton-phonon scattering are considered and an interpolation formula for the diffusion coefficient valid in all interesting temperature and concentration regions is presented. A comparison with the experimental data is made. Some alternative points of view are discussed in detail and the inconsistency of the Kisvarsanyi-Sullivan theory is shown.

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Section: Defecton-defecton Scatteringmentioning

confidence: 99%

“…The quantity σ for the potential (16) with n = 3 in quasiclassical approximation is of the form [30,2] …”

Section: Defecton-defecton Scatteringmentioning

confidence: 99%

Section: Phonon Controlled Diffusionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…by means of nuclear magnetic resonance (NMR) [10]. [2,11]. The degeneracy temperature T 0 is extremely small:…”

Section: Introductionmentioning

confidence: 99%

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Quantum diffusion

Pushkarov

2004

Open Physics

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Bottom-Up Approaches in Physics

Primas

2017

Knowledge and Time

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Statistical mechanics of structural fluctuations

Yukalov

1995

Physica A: Statistical Mechanics and its Applications

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The theory of mesoscopic fluctuations is applied to inhomogeneous solids consisting of chaotically distributed regions with different crystalline structure. This approach makes it possible to describe statistical properties of such mixture by constructing a renormalized Hamiltonian. The relative volumes occupied by each of the coexisting structures define the corresponding geometric probabilities. In the case of a frozen heterophase system these probabilities should be given a priori. And in the case of a thermal heterophase mixture the structural probabilities are to be defined self-consistently by minimizing a thermodynamical potential. This permits to find the temperature behavior of the probabilities which is especially important near the points of structural phase transitions. The presense of these structural fluctuations yields a softening of a crystal and a decrease of the effective Debye temperature. These effects can be directly seen by nuclear gamma resonance since the occurrence of structural fluctuations is accompanied by a noticeable sagging of the Mössbauer factor at the point of structural phase transition. The structural fluctuations also lead to the attenuation of sound and increase of isothermic compressibility. I. INTRODUCTIONThere are many examples of matter consisting of regions, chaotically distributed in space, with different structural properties. For instance, such are some polymorphic materials. Another example is a crystal subject to strong mechanical stress after which the cracks and branches of dislocation are formed in it. These defects have a tendency to group inside compact regions. The latter, from the point of view of statistical physics, can be treated as nuclei of the amorphised phase inside a crystalline matrix [1]. A similar picture develops in crystals under the action of irradiation by fast neutrons when the pores and regions of disorder arise. Under strong irradiation cracks also appear. These defects form groups and clusters randomly distributed in space, e.g. as is shown in Figs. 1 and 2. For a statistical description of an irradiated crystal the defected regions can be treated as embryos of disordered, usually rarefied, phase inside an ordered, more dense, crystalline structure [2,3]. The relative volume occupied by the disordered phase can be measured, with a good accuracy, by investigating the nuclear gamma resonance spectra and the behavior of the Mössbauer factor [4,5].In the considered examples the germs of a disordered structure are randomly distributed in space inside an ordered structure. This is why these germs can be called the spatial structural fluctuations. With respect to time, they are frozen, which means that their average lifetime, τ f , is much longer than the characteristic time of an experiment, or the observation time, τ obs , that is: τ f ≫ τ obs . In the opposite case, when τ f ≪ τ obs , we have thermal structural fluctuations. The example of the latter are even more numerous than those of the frozen structural fluctuations.Water, the most widespr...

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Quasiparticle Theory of Defects in Solids

Cited by 19 publications

References 0 publications

Quantum diffusion

Quantum diffusion

Bottom-Up Approaches in Physics

Statistical mechanics of structural fluctuations

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