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[ISSP Colloquiums]
Attempts at magnetism on the kagome lattice
Title : Attempts at magnetism on the kagome lattice
Date :
Time :
4:00 PM - 5:00 PM 
Place : Lecture Room (A632), 6th Floor, ISSP   
Lecturer : Prof.Collin Broholm
Affiliation : Johns Hopkins University
Summary : While no ideal model system has yet been identified, kagome related spin systems consistently
show interesting strongly correlated physics associated with frustration, weak connectivity,
and quantum fluctuations. Here I compare and contrast several different kagome systems as I
review the corresponding neutron scattering experiments.
The spin-3/2 systems SCGO and QS-ferrite, which do have quenched disorder, achieve a curious
short range ordered state of frozen antiferromagnetic clusters that support coherent linearly
dispersive modes [1]. In Ni3V2O8 buckling of the kagome
lattice produces incommensurate long-range order with concomitant ferroelectricity [2]. In
Rb2Cu3SnF12 dimerization yields a singlet ground state with
excited state singlets and doublets due to DM interactions [3]. In synthetic Herbert Smithite,
which contains spin-1/2 copper on the vertices of an ideal kagome lattice, we find lines of
scattering in momentum space [4] consistent with expectations for de-confined spinons [5].
The experiments expose a wide range of unconventional magnetism while protecting the mystique
surrounding the ground state of the ideal spin-1/2 kagome antiferromagnet.

[1] "Antiferromagnetic Fluctuations and Short Range Order in a Kagome Lattice", C. Broholm,
et al., Phys. Rev. Lett., 65, 3173 (1990).
[2] "Magnetically Driven Ferroelectric Order in Ni3V2O8", G. Lawes et al., Phys. Rev. Lett. 95,
087205 (2005).
[3] "Pinwheel valence-bond solid and triplet excitations in the two-dimensional deformed
kagome lattice", K. Matan, et al., Nature Physics 6 865-9 (2010).
[4] Work done in collaboration with Tianheng Han, Joel S. Helton, Jose A. Rodriguez-Rivera, and
Young S. Lee (2011).
[5] "Fermionic Spin Excitations in Two- and Three-Dimensional Antiferromagnets," Zhihao Hao
and Oleg Tchernyshyov, Phys. Rev. Lett. 103, 187203 (2009)

Committee: Masaki Oshikawa,Yohei Kobayashi(