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http://hdl.handle.net/1783.1/3661
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| Title: | Heisenberg model with spin anisotropy on the Kagomé lattice |
| Authors: | Fong, Manson Cheuk-Man |
| Issue Date: | 2008 |
| Abstract: | The successful synthesis of ZnCu3(OH)6Cl2 has provided a long-awaited opportunity to test experimentally the physics of spin-1/2 Heisenberg antiferromagnet on the kagomé lattice, which is a frustrated network with a low coordination number. The compound has a coupling constant J ~ 170K, and it does not show any magnetic order down to 50mK. However, from electron spin resonance (ESR), the Dzyaloshinskii-Moriya (DM) interactions which favor the three-sublattice Q = 0 Néel order, are found to be present, with strength D ~ 0.08J. By using exact diagonalization, we obtain the low-lying spectra of the spin Hamiltonian on periodic clusters up to 36 sites. We also calculate the sublattice moment in each cluster. Then with finite-size scaling, we argue that in the thermodynamic limit, the Heisenberg antiferromagnet with DM interactions undergoes a quantum phase transition at Dc ~ 0.1J. For D < Dc, the system has no magnetic long-range order; for D > Dc, it develops the Q = 0 Néel order. Our results are therefore compatible with the absence of Néel-type order found experimentally in ZnCu3(OH)6Cl2, where D is only ~ 0.08J. |
| Description: | Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2008
xi, 74 p. : ill. (some col.) ; 30 cm
HKUST Call Number: Thesis PHYS 2008 Fong |
| URI: | http://hdl.handle.net/1783.1/3661 |
| Appears in Collections: | PHYS Master Theses
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