大型放射光施設 SPring-8

日   時 ： 2004年2月17日　16：00 -

講演者 ： Dr. Karlo Penc
所   属 ： Research Institute for Solid State Physics, Budapest, Hungary

講演要旨
　　The quarter-filled Hubbard model extended with nearest neighbor repulsion on the pyrochlore lattice is an insulator for sufficiently large couplings, with an extensive ground state degeneracy. The model can be mapped to the ice- and the 6-vertex problems.
　　The large degeneracy in the ground state manifold can support topological excitations with e/2 charge. Quantitative results are presented for the two-dimensional bosonic version of the problem, the XXZ Heisenberg model, where we discuss the effect of quantum fluctuations and the spinon deconfinement.