Classical and quantum transport on square lattices and disordered clusters in two dimensions
Abstract
The transport of a particle through disordered clusters can be treated either classically or quantum mechanically, depending on the size of the systems involved. In this thesis we employ both treatments. In the classical part we extend ordinary site percolation on a square lattice to fully coordinated (FC) percolation and to iterated fully coordinated (IFC) percolation models. FC percolation comes about by adding a full coordination requirement to ordinary site percolation. In IFC percolation we iterate this requirement one more time. We find all three models to belong to the same universality class. We also find a developing Euclidean signature as we iterate the models from ordinary to FC and then to IFC percolation. In the quantum part we study the transmittance of a particle traversing through square lattices and through disordered clusters. The square lattices and disordered clusters are attached to two semi-infinite chains serving as the input and output leads. The leads and the clusters are coupled together through either point to point contacts or busbar connections. In transport through square lattices we find resonant transmission and reflection whenever the energy of the incident particle is close to a doubly-degenerate eigenvalue of the uncoupled lattice. We also find the transmission to be sensitive to the type of coupling chosen. In transport through disordered clusters we find the transmission to decrease as the clusters become larger. This hints that states are localized. Furthermore, we find the transmission to be independent of the coupling chosen in the presence of strong disorder. This independence is lost in weakly disordered clusters. We also find hints of localized-to-localized transitions as we vary the degree of disorder. However, the clusters we have been studying are still too small to make definite conclusions. We thus find it necessary to extend our analyses to larger-sized clusters.
Degree
Ph.D.
Advisors
Nakanishi, Purdue University.
Subject Area
Condensed matter physics
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.