Optical excitations in systems with frustrated lattice topology

• Applicant: Dr. Joachim Deisenhofer
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2012 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 198233866

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.

• DFG Programme: Research Grants