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The Spin-wave Excitations of the Collinear Antiferromagnetic Phase in Iron Pnictides

Author: LiuYang
Tutor: DaiJianHui
School: Zhejiang University
Course: Theoretical Physics
Keywords: Iron-based superconductors J1-J2 model J1-J2 matrix model Structural phase transition Antiferromagnetic phase transition Ground state energy Spin wave excitations
CLC: O469
Type: Master's thesis
Year: 2009
Downloads: 71
Quote: 0
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Abstract


The discovery of the new iron-based high-temperature superconductors has attracted the keen interest of scientists . A notable feature of these materials is that the parent compound occurs at low temperature, the structural phase transition and the anti - ferromagnetic phase transition . Electron or hole doping the parent compound , the structural phase transition and the antiferromagnetic phase transition will be suppressed , thus contributing to the generation of high-temperature superconductivity . It is widely believed that the generation of the superconducting and magnetic frustration should be intrinsically linked to the magnetic frustration is likely to lead to the structural phase transition and the antiferromagnetic phase transition . In this paper , we will study the antiferromagnetic spin wave excitations below the phase transition temperature . In the first chapter , we review the discovery and study of the course of high-temperature superconductivity , and focus on understanding the status and the progress made in iron-based high-temperature superconductivity . In the second chapter , we introduced the structure , the nature and classification of the iron-based superconducting materials , focus on the same features and the different characteristics of the iron-based superconductor and copper oxide superconductors . In the third chapter , there is frustration on the basis of the two-dimensional Heisenberg J1-J2 model to analyze the nature of the 2D striped antiferromagnetic state low temperature magnetic excitation . We also analyzed the phase diagram of the ground state of the system , the the stripe antiferromagnetic state and spin fluctuations . The fourth chapter is the main part of my thesis . In this chapter , we expand the J1-J2 model , including the model of anisotropic J1-J2 and J1-J2 matrix model . We also analyzed the change of the phase diagram , the energy of the ground state and the spin -wave dispersion relation . The fifth chapter summarizes and comments .

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