Estudo da dinâmica de alguns modelos antiferromagnéticos unidimensionais.
Ano de defesa: | 2009 |
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Autor(a) principal: | |
Orientador(a): | |
Banca de defesa: | |
Tipo de documento: | Tese |
Tipo de acesso: | Acesso aberto |
Idioma: | por |
Instituição de defesa: |
Universidade Federal de Minas Gerais
UFMG |
Programa de Pós-Graduação: |
Não Informado pela instituição
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Departamento: |
Não Informado pela instituição
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País: |
Não Informado pela instituição
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Palavras-chave em Português: | |
Link de acesso: | http://hdl.handle.net/1843/ESCZ-7ZEFSV |
Resumo: | We present the low-temperature dynamic properties of the quantum one-dimensional Heisenberg antiferromagnet with integer Spin S with spin-phonon interaction, Dzyaloshins-kii-Moriya interaction and taking into account three magnon processes. First, we present the low-temperature dynamic properties of the quantum one-dimensionalHeisenberg antiferromagnet with integer spin S coupled to phonons. The calculation of the relaxation function is performed using the combination of the memory function formalism with the modified spin-wave theory. The procedure includes up to two-magnon and magnon-phonon processes. We show that the magnon-phonon coupling smooths the double-peak structure obtained for the model in the absence of phonons, when the wavevector q moves from q = ¼. After that, we present a calculation of the in-plane dynamical structure factor for the S = 1 one-dimensional antiferromagnet with a Dzyaloshinskii-Moriya interaction using the Schwinger boson mean-field theory. Then, we present the dynamical properties of the Heisenberg antiferromagnet takinginto account three magnon processes. We calculate the correlation function in time using the modified spin-wave theory. The procedure here includes up to two and three-magnon processes. We show that the double peak structure obtained for the model taking into account two-magnon processes is not smoothed when we take account three-magnon processes too |