Fluctuations and dissipation of collective dynamics in spin and pseudospin ferromagnets

dc.contributor.advisorMacDonald, Allan H.en
dc.creatorRossi, Enricoen
dc.description.abstractIn this thesis a careful study of the equilibrium and transport properties of ν = 1 quantum Hall bilayers is presented. Our approach is based on the pseudospin analogy in which the layer degree of freedom for the electrons is treated as a spin degree of freedom. This treatment reveals the many analogies between these systems and spin systems. After briefly reviewing the basic physics of the quantum Hall effect in chapter 2, in chapter 3 we introduce the quantum Hall bilayer systems and define the pseuduspin model used in the following chapters to study their properties. In chapter 4 we present our results on the equilibrium properties of quantum Hall bilayers in presence of strong disorder. In particular we calculate the critical disorder strength above which the interlayer phase coherence is lost, and the Kosterlitz-Thouless temvi perature goes to zero. In chapter 5 we develop a theory for the tunneling transport in these systems. In contrast to most previous theoretical work our theory predicts that the zero bias conductance is finite even in a perfect disorder free bilayer at zero temperature and accounts, within an order of magnitude, for the width of the anomaly observed in experiments. Also the theory correctly predicts the suppression of the tunneling conductance in presence of a magnetic field in the plane of the 2DEG. Using the results of chapter 4 the theory can also quantify the suppression of the tunneling conductance due to disorder. In chapter 6 we study the dynamics of the magnetization when coupled to a thermal bath of elastic modes. We derive explicit expressions for the memory friction kernel and the spectral density of the fluctuations starting from a realistic form of the coupling of the magnetization to the elastic modes. Finally in chapter 7 we study the dynamics of a particularly interesting class of collective modes in magnetized plasmas: tearing modes. We develop a rigorous approach to describe the evolution of these modes beyond the linear approximation. Using this approach we then consider nonlinear effects due to the coupling of the fundamental mode to higher harmonics and external perturbations.
dc.rightsCopyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.en
dc.subject.lcshQuantum Hall effecten
dc.titleFluctuations and dissipation of collective dynamics in spin and pseudospin ferromagnetsen
thesis.degree.grantorThe University of Texas at Austinen
thesis.degree.nameDoctor of Philosophyen

Access full-text files

Original bundle

Now showing 1 - 1 of 1
Thumbnail Image
3.21 MB
Adobe Portable Document Format

License bundle

Now showing 1 - 1 of 1
No Thumbnail Available
1.65 KB
Plain Text