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Darshan Joshi (Max-Planck Institute, Stuttgart, Germany)
Date & Time
Wed, 09 January 2019, 14:30 to 15:30
Emmy Noether Seminar Room, ICTS Campus, Bangalore

Many frustrated magnets host exotic states of matter with non-trivial ground states. We show that in certain systems even if the ground-state is trivial one can realize exotic phases by the virtue of  non-trivial topological excitations. These topological excitations are  in a way analogs of the fermionic topological states of matter, albeit  with many differences. We shall show that the paramagnetic phase of  coupled-dimer systems on a ladder as well as a honeycomb bilayer  support topological excitations in the presence of spin-orbit  coupling. These excitations are localized at the edges and in case of  the ladder they are even fractionalized. We discuss relevant  observables, topological invariants, and possible experimental  signatures. Another important example, namely the Kitaev-Heisenberg model, will be shown to host chiral edge excitations. In this case, we  will discuss interplay between external magnetic field and  spin-asymmetric interaction. In all the cases, we shall show that  there is a well-defined tuning parameter (eq. field, pressure) which  can be used to also study a topological quantum phase transition.