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Miyahara, Shin

Ueda, Kazuo

Yamashita, Yasufumi

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Title Two- and three dimensional frustrated spin systems(NewDevelopments in Strongly Correlated Electron Systems)Author(s)Ueda, Kazuo; Miyahara, Shin; Yamashita, YasufumiCitation物性研究 (2001), 76(5): 691-691Issue Date2001-08-20URL http://hdl.handle.net/2433/97043RightType Departmental Bulletin PaperTextversionpublisherKyoto UniversityiNew Developments in Strongly Correlated Electron SystemsJTwo- and three dilnensional frustrated spin systenlsKazuo Ueda, Shin Miyahara and Yasufulni YanlashitaInstitute for Solid State Physics, University of TokyoKashiwa-no-ha 5-1-5, Kashiwa-si, Chiba 277-8581, JapanIn this presentation I will discuss recent developlnents on frustrated spinsystenls in two and three ditnension: the orthogonal dilller spin system andthe 8==1 Pyrochlore systenl.The two dimensional Heisenberg lllodel for 8rCu2(BOah has the exactdimer ground state which was proven by Shastry and Sutherland alnlosttwenty years ago. Almost localized nature of the triplet excitations explainsthe plateaus observed in the 111agnetization and unusual dynaillical propertiesof the low lying excitations.The ground-state properties of the spin-1 antifelTolnagnetic Heisenberg11lodel on the corner-sharing tetrahedra, pyrochlore lattice, is investigated.By breaking up each spin into a pair of 1/2-spins, the problern is reduced tothe equivalent one of the spin-1/2 tetrahedral network in analogy with thevalence bond solid state in one diluension. The twofold degeneracy of thespin-singlets of a tetrahedron is lifted by a Jahn-Teller Inechanism, leadingto a cubic to tet~agonal structural transition. It is proposed that the presentnlechanisln is responsible for the phase transition observed in the spin-1 spinelcOlnpound ZnV2 0 4 and rvrgV2 0 4 .- 691 -

Two- and three dimensional frustrated spin systems(New Developments in Strongly Correlated Electron Systems)

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Two- and three dimensional frustrated spin systems(New Developments in Strongly Correlated Electron Systems)

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