講演者: Karlo Penc 教授
The Institute for Solid State Physics and Optics, Wigner Research Centre for
Physics, Hungarian Academy of Sciences
日時: 2016 年 7 月 1 日(金) 午後 2 時 40 分 〜 3 時 40 分
場所: 学習院大学南 7 号館 4 階会議室
（山手線目白駅から徒歩で約 3 分）
目白駅の唯一の改札を出て右に向かい横断歩道を渡れば、目の前が学習院大学の西門。
方向感覚の悪い人でも迷いません（道順はこちら）
SrCu2(BO3)2 is the archetypal quantum magnet with a gapped dimer- singlet ground state and triplon excitations. It serves as an excellent realization of the Shastry Sutherland model, up to small anisotropies arising from Dzyaloshinskii Moriya (DM) interactions. We demonstrate that the DM couplings in fact give rise to topological character in the triplon band structure. The triplons form a new kind of a Dirac cone with three bands touching at a single point, a spin-1 generalization of graphene. An applied magnetic field opens band gaps leaving us with topological bands with Chern numbers ±2. SrCu2(BO3)2 is thus a magnetic analogue of the integer quantum Hall effect and supports topologically protected edge modes. At a critical value of the magnetic field set by the strength of DM interactions, the three triplon bands touch once again in a spin-1 Dirac cone, and lose their topological character. We predict a strong thermal Hall signature in the topological regime.
責任者(物理学科:宇田川 将文)
