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Title:Theory of polaron mobility
Author(s):Langreth, David Chapman
Doctoral Committee Chair(s):Kadanoff, L. P.
Department / Program:Physics
Subject(s):polaron mobility
polaron-phonon system
quasiparticle states
Green's functions
Abstract:Two different methods for describing the polaron-phonon system are formulated 0 These are: (1) description in terms of quasiparticle states, (2) description in terms of thermodynamic GreenYs functions~ The first approach leads naturally to an S matrix formulation of polaron transport~ The second leads to the Kadanoff-Baym transport equations 0 It is shown that both approaches are equivalento By using the latter approach$ it is shown that the low-temperature polaron drift mObility is given rigorously by IJ. :; e'T/m * , where 'T is the polaron lifetime" and m* its effective masso This relationship is verified explicitly to lowest nontrivial order in the coupling constant by using the Kubo formula. Various methods for calculating the low-temperature mobility for weak and intermediate coupling are discussed and critically compared~ These methods include: (1) perturbation theorYt (2) the Feynman model of the polaron as applied by 'osaka, or Feynman, Hellswarth, Iddings, and Platzman» or Schultz, (3) the Low-Pines intermediate coupling theory augmented by Lawus scattering theory 0 The low=temperature mobility is calculated in pertur- 02· bat ion theory to order a. 0 It is found that I-L = lJ.o (l=a/6 + 0(0, UJI where Il o is the weak~coupling mo. bilityo This result corresponds most closely with the expansion of Osakavs mobility formula o Certain improvements to the mobility calculations of Schultz~ and of Low and Pines are suggested 0 When these improvements are incorporated» both the Low~Pines and the Schultz theories come into much better agreement with the perturbation expansion for weak coupling, and wit.h OsakaBs theory for intermediate coupling.
Issue Date:1964
Genre:Dissertation / Thesis
Rights Information:1964 David Chapman Langreth
Date Available in IDEALS:2011-05-18
Identifier in Online Catalog:6146096

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