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TT: Fachverband Tiefe Temperaturen

TT 1: Focus Session: Frustration in Mott Insulators and Mott Criticality

TT 1.2: Hauptvortrag

Montag, 20. März 2017, 10:00–10:30, HSZ 03

Anisotropic Magnetism and Spin Gap in α-RuCl₃ — •Bernd Büchner — IFW Dresden, Helmholtzstraße 20, 01069 Dresden

Quantum spin liquids are a central theme in current condensed matter physics as they host emergent topological order and fractionalized excitations. An important example are interacting Kitaev spins on a honeycomb lattice which are theoretically predicted to exhibit topological and quantum spin liquids. Identifying signatures of Kitaev physics, however, is extremely challenging as real materials, such as the iridates (Na,Li)₂IrO₃, inevitably entail an isotropic Heisenberg and additional spin-exchange interactions, thereby stabilizing a magnetically ordered state. Hexagonal Ru trichloride α-RuCl₃ has been recently reported to be near the Kitaev spin-liquid phase boundary. The layered honeycomb structure of α-RuCl₃ contains layers weakly coupled by van der Waals interaction, i.e. it is a correlated 2d-material offering many possibilities for *materials engineering*. We have characterized the electronic and magnetic properties of α-RuCl₃ by a broad spectrum of experimental techniques. From electron spectroscopy basic parameters determining the insulating state of α-RuCl₃ are extracted. Moreover, strongly anisotropic magnetic properties as measured from magnetization, specific heat, thermal conductivity, and NMR measurements will be presented and discussed. Both, the behavior of α-RuCl₃ in the paramagnetic phase as well as the properties of the ordered state strongly differ from that found in conventional two-dimensional magnets. In particular, we find a very unusual field-temperature phase diagram with evidence for a novel quantum critical point.