Theory of polaron mobility

"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."

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2011

Author dc:creator

• Langreth, David Chapman

Contributors dc:contributor

• Kadanoff, L.P.

• polaron mobility
• polaron-phonon system
• quasiparticle states
• Green's functions

Statement dc:rights

• 1964 David Chapman Langreth

Language dc:language

en

Identifier

6146096

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/23954