Optical excitations in systems with frustrated lattice topology

光学和太赫兹光谱将在铬基体系中进行，其中磁性Cr3+离子占据几何受阻晶格，特别是在反铁磁性氧化物尖晶石ACr2O4(A=Zn，Mg，Cd，Hg)的情况下，焦绿石晶格和具有A=Cu，Ag，Pd和X=O，S，Se的化合物ACrX2的二维三角晶格。我们将探讨自旋和晶格自由度的耦合及其对提升磁性基态宏观简并度的影响，以及与经典自旋-液态区中有限自旋关联的关系。磁激发谱将通过光学活性激子-磁振子跃迁获得，磁振子边带的寿命将分别与三角形化合物和焦绿石化合物中拓扑保护的Z2涡旋或六方自旋分子的形成有关。

Optical and THz spectroscopy will be performed in Cr based systems where the magnetic Cr3+ ions occupy geometrically frustrated lattices, in particular a pyrochlore lattice in the case of the antiferromagnetic oxide-spinels ACr2O4 (A= Zn, Mg, Cd, Hg) and a two-dimensional triangular lattice for compounds ACrX2 with A = Cu, Ag, Pd and X = O, S, Se. The coupling of spin and lattice degrees of freedom and its effects on lifting the macroscopic degeneracy of the magnetic ground state and the relation to the finite spin correlations in the classical spin-liquid regime will be explored. The magnetic excitation spectrum will be accessed via optically active exciton-magnon transitions and the lifetime of the magnon sidebands will be investigated with respect to the formation of topologically protected Z2 vortices or hexagonal spin-molecules in the triangular and pyrochlore compounds, respectively.