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Special Seminar: Frustrated 2D Magnetism in 3He Monolayer: Spin liquid phase stabilized by many-body exchange interactions

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Hiroshi Fukuyama, University of Tokyo
When
10 November 2014 from 4:00 PM to 5:00 PM
Where
339 Davey Laboratory
Contact Name
Milton Cole
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The spin liquid phase is a new class of magnetic ground state in nature. This is the S = 0 state without apparent long-range ordering even at absolute zero. During the last decade several candidate materials have been studied extensively including quasi two-dimensional (2D) organic materials (κ-(BEDT-TTF)2Cu2(CN)3, EtMe3Sb[Pd(dmit)2]2) and some oxides with hyperkagome structure (Na4Ir3O8) [1]. The common feature behind them is that they are antiferromagnetically interacting quantum spin systems with geometrical frustration of low coordination numbers. Beside those electronic systems there exists another spin liquid candidate of nuclear spin. It is the strictly 2D nuclear spin system (I = 1/2) on a triangular lattice realized in monolayer solid of 3He physisorbed on graphite. The unique feature in this system is that the direct atom-atom exchange interaction is not restricted only to two-spin exchange but three-, four-, five- and six-spin exchanges are competing in comparable magnitudes (|Jn| ≈ 10 mK). Here even (odd) numbers of exchanging atoms favor antiferromagnetic (ferromagnetic) interactions. The competition, together with the frustrated geometry, seems to be providing the gapless spin liquid state below 1 mK. In this talk, I will overview recent progress in studies of the frustrated magnetism in 2D solid 3He as well as some future prospects.

[1] L. Balents, Nature 464, 199 (2010) and references therein.

[2] H. Fukuyama, J. Phys. Soc. Jpn. 77, 111013 (2008) and references therein.

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