Transport studies and phenomenological model for sliding charge-density waves in quasi-one-dimensional conductors
Lyons, William Gregory
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https://hdl.handle.net/2142/20325
Description
Title
Transport studies and phenomenological model for sliding charge-density waves in quasi-one-dimensional conductors
Author(s)
Lyons, William Gregory
Issue Date
1989
Doctoral Committee Chair(s)
Tucker, John R.
Department of Study
Electrical and Computer Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Physics, Condensed Matter
Language
eng
Abstract
Transport studies examining the dynamics of one-dimensional charge-density wave (CDW) condensates are reported. Results using rf and dc, linear and nonlinear electrical transport techniques have been obtained at temperatures below the CDW transition in the quasi-one-dimensional materials o-TaS$\sb3$, K$\sb{0.03}$MoO$\sb3$, (IaSe$\sb4)\sb2$I and NbSe$\sb3$. Each of these materials exhibits a different set of CDW parameters due to differences in structural properties and electronic band structure. By correlating results obtained on these four materials systems and by considering a detailed overview of other experimental work in the field, the generic features of charge-density wave dynamics have been elucidated.
A phenomenological model based on strong impurity pinning of the CDW phase is presented as a possible framework for resolving a long-standing debate over the correct theoretical description for CDW transport. Essentially all of the experimental results known to date on CDW systems can be interpreted within this framework. Numerical estimates are made from the model accurately reproducing the observed generic features of CDW dynamics. A brief summary is made of the shortcomings that have faced various other classical and quantum mechanical models. The study provides a solid reference point for future advances in microscopic charge-density wave theory.
Sliding CDWs constitute only the second known example of a moving quantum ground state, the first being superconductivity. Unlike superconductivity, sample impurities break the translational invariance of an incommensurate CDW and pin it to the underlying crystal lattice. The universal features of the dynamics seen in CDW conductors are indeed very rich. Nonlinear conductivity occurs above a dc threshold for both deformable motion at high temperatures and rigid motion in fully gapped materials at low temperature. The ac response of the pinned CDW has a very complex behavior with up to three characteristic pinning frequencies and associated damping constants. Dielectric relaxation proves to be the most important element in properly describing the CDW phase dynamics, including motion of the charge-density wave in the periodic impurity pinning potential.
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