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Identifier 000390009
Title Dynamics of field-induced phases in spin-1 antifferomagnetic chains
Alternative Title Δυναμική μαγνητικού πεδίου επαγώμενων φάσεων σε S=1 αντισιδηρομαγνητικές αλυσίδες
Author Ψαρουδάκη, Χριστίνα
Thesis advisor Ζώτος, Ξενοφών
Παπανικολάου, Νικόλαος
Abstract This thesis is devoted to the study of a class of antifferomagnetic spin-1 chains with a strong easy plane anisotropy in the presence of magnetic field. At zero temperature the system undergoes two quantum phase transitions at critical fields. Reliable and detailed theoretical analysis is provided on the Electron Spin Resonance (ESR) spectrum, thermodynamics and the thermal transport of the model. The tools at hand range from exact analytical solutions and to numerical simulation techniques. The S=1 antiferromagnet in a magnetic field can be systematically mapped onto an S=1/2 ΧΧΖ chain in a longitudinal magnetic field. This effective S=1/2 description has been extensively used in order to gain a better physical understanding of the original S=1 chain. For the Electron Spin Resonance spectrum, apart from the theoretical analysis, high-field ESR experimental studies of the compound NiCl2 - 4SC(NH22)22 (abbreviated as DTN) are presented and found consistent with theoretical predictions. The most interesting feature is the experimental signature of the single-ion two-magnon bound state. Part of this thesis is devoted to the magnetic-field and temperature dependence of magnetization and specific heat for the whole field-region and a wide range of temperatures, with special emphasis at the critical behaviour of these quantities at the critical fields. Finally, the calculation of dynamic correlation functions pertinent to the study of thermal transport is addressed for the S=1 model with easy plane anisotropy and the S=1/2 XXZ model in the presence of finite magnetic field.
Language English
Subject Electron spin resonance
Quantum magnetism
Spin chains
Thermal transport
Αλυσίδες σπιν
Κβαντικός μαγνητισμός
Issue date 2014-12-22
Collection   School/Department--School of Sciences and Engineering--Department of Physics--Doctoral theses
  Type of Work--Doctoral theses
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