Wednesday, January 11, 2017
Mott insulators are of central importance in condensed matter physics because they often host exotic magnetic ground-states and excitations. This is particularly true for spin-liquids, correlated yet fluctuating states of magnetic matter stabilized by e.g. low-dimensionality, geometrical frustration, spin-orbit coupling and/or disorder. As for conventional liquids, both classical and quantum spin-liquids exist and a central question is to determine the nature of the quasiparticles governing their dynamics. I will present inelastic neutron scattering investigations from a selection of single-crystalline magnetic materials [1,2,3] and address how to distinguish quantum from classical spin-liquids from their dynamical responses.
 M. Mourigal, M. Enderle, A. Klopperpieper, J.-S. Caux, A. Stunault, and H. M. Rønnow. Fractional spinon excitations in the quantum Heisenberg antiferromagnetic chain, Nature Physics 9, 435-441 (2013).
 J. A. M. Paddison, M. Daum, Z. L. Dun, G. Ehlers, Y. Liu, M. B. Stone, H. D. Zhou, and M. Mourigal, Continuous excitations of the triangular-lattice quantum spin liquid YbMgGaO4, arXiv:1607.03231 (2016).
 X. Bai, M. Mourigal et al., Spin excitations in the pyrochlore-lattice Heisenberg antiferromagnet MgCr2O4, in preparation (2016).