物理科学科セミナーご案内（2008年12月24日）
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| 日時 | 2008年12月24日（水）17：30～18：30 |
|---|---|
| 場所 | 京都産業大学理学部会議室（2号館3階） |
| 講演者 | Karlo Penc 氏 （京都大学基礎物理学研究所客員教授・Research Institute for Solid State Physics and Optics (RISSPO) ハンガリー） |
| 講演題目 | Quadrupolar Phases of the S=1 Heisenberg Model on the Triangular and Square Lattice |
講演概要
Using mean-field theory, exact diagonalizations, and SU(3) flavor theory, we have mapped out the phase diagram of the S=1 bilinear-biquadratic Heisenberg model on the triangular and square lattice in a magnetic field, with emphasis on the quadrupolar phases and their excitations. In particular, we find several plateaux phases in these models: the antiferroquadrupolar phase in the triangular lattice is characterized by a remarkable 2/3 magnetization plateau, in which one site per triangle retains quadrupolar order while the other two are polarized along the field. In the square lattice a two sublattice 1/2 plateaux develops, and at zero field the quantum fluctuations stabilize a 3-sublattice order. We also show examples of quadrupolar (nematic) ordering in classical spin system in pyrochlore lattice.
