Seminar by Karlo Penc: "Triplon Hall effect in the SrCu2(BO3)2"
Date : Thursday, 17th April
Time : 13:00 - 14:30
Venue : D014, Lab1
Speaker : Prof. Karlo Penc
Title : Triplon Hall effect in the SrCu2(BO3)2
We demonstrate that SrCu2(BO3)2, the well known realization of the Shastry-Sutherland model, in fact hosts the magnon Hall effect. The Shastry-Sutherland model has an exact dimer singlet ground state. However, the material SrCu2(BO3)2 has small Dzyaloshinskii-Moriya interactions which admix a triplet component into the ground state. The resulting state has small magnetic moments and its lowest excitations are three gapped magnon modes, well described by triplons (the triplet states on the dimers). An applied magnetic field splits these modes and opens band gaps. Surprisingly, we are left with topological magnon bands with non-zero Chern numbers. Thus, SrCu2(BO3)2 supports protected magnonic edge modes and is a magnetic analogue of the integer quantum Hall effect. Ultimately, this topological character stems from the Dzyaloshinskii-Moriya interactions which generate a Lorentz force for magnons. We discuss possible experimental probes, inluding the thermal Hall effect to test this theory.