Fluctuation conductivity from charge density waves in pseudo-one-dimensional systems

This thesis examines theoretically the Fröhlich conductivity model, which describes a charge-density-wave phenomenon which can lead to enhanced electrical conductivity in pseudo-one-dimensional systems. The experimental facts concerning pseudo-one-dimensional systems which may illustrate aspects of the Fröhlich mechanism are reviewed. The physical basis of the Fröhlich model is discussed in detail and is extended by the new suggestion that the important Fröhlich mode frequencies are less than the Kohn anomaly frequency. A phenomenological formulation of the free energy is used to calculate the fluctuation electrical conductivity (paraconductivity) at temperatures where the fluctuations are still mobile. The result gives values which are somewhat small to account for the largest experimental results. The fluctuation thermal conductivity is calculated similarly, and its ratio to the paraconductivity is found to be suppressed, very much as in the BCS model. A microscopic model is introduced through the formulation of the Fröhlich collective mode propagator, approximations to which are examined for deficiencies. An approximation to the propagator is used to calculate diagrammatically the paraconductivity. An attempt is made to resolve disagreement in the literature regarding this calculation, and the correspondence of the mic,oscopic and phenomenological results is discussed. The use of mean-field theory in one dimension limits the validity of these calculations to several degrees above the transition temperature.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2012

Author dc:creator

• Bray, James William

Contributors dc:contributor

• Bardeen, John

• fluctuation conductivity
• charge density waves
• pseudo-one-dimensional systems
• Fröhlich conductivity model

Statement dc:rights

• Copyright 1974 James W. Bray

Language dc:language

en

Identifier

2638819

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/30727