Magnetism is one of the most ubiquitous collective phenomena in condensed matter physics. In frustrated magnets, the inability to satisfy the local interactions globally can suppress conventional forms of magnetic order and expose new states of matter. This can include unusual magnetic and non-magnetic orders as well as disordered states such as spin liquids. The simplest route to such frustration is geometric, realized by Heisenberg antiferromagnets on lattices built from triangles, such as in the triangular, kagome or pyrochlore lattices. In this talk I will discuss an alternative route that has attracted recent interest: frustration through anisotropic interactions. Such anisotropy naturally arises in materials where the magnetic ions have strong spin-orbit coupling, such as in rare-earths or heavy transition metals. I will survey recent theoretical and experimental efforts to realize to a paradigmatic example: Kitaev's honeycomb model, in 4d and 5d transition metal oxides. I will outline some challenges in finding the expected spin liquid ground state, and some properties of its unconventional magnetic ordering and excitations. Finally, I will discuss some recent tantalizing hints that the spin liquid phase, and it's associated Majorana excitations, may re-emerge in a the presence of a magnetic field.
https://umontreal.zoom.us/j/4074103908?pwd=NUNpcXVueGRMTFVhdHRvZFpvaFNDdz09
Identifiant: 407 410 3908
Mot de passe: trois quatre trois six un un un
