title: Hall effect of triplons in a dimerized quantum magnet.
abstract: SrCu2(BO3)2 is the archetypal quantum magnet with a gapped dimer-singlet ground state and triplon excitations. It serves as an excellent realization of the Shastry-Sutherland model, up to small anisotropies arising from Dzyaloshinskii-Moriya interactions. Here we demonstrate that these anisotropies, in fact, give rise to topological character in the triplon band structure. The triplons form a new kind of Dirac cone with three bands touching at a single point, a spin-1 generalization of graphene. An applied magnetic field opens band gaps resulting in topological bands with Chern numbers ±2. SrCu2(BO3)2 thus provides a magnetic analogue of the integer quantum Hall effect and supports topologically protected edge modes. At a threshold value of the magnetic field set by the Dzyaloshinskii-Moriya interactions, the three triplon bands touch once again in a spin-1 Dirac cone, and lose their topological character. We predict a strong thermal Hall signature in the topological regime.
authors: Leibniz-Institute for Solid State and Materials Research, IFW-Dresden, D-01171 Dresden, Germany.
authors: Judit
authors: J
authors: Romhányi
authors: Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, PO Box. 49, H-1525 Budapest, Hungary.
authors: Karlo
authors: K
authors: Penc
authors: Leibniz-Institute for Solid State and Materials Research, IFW-Dresden, D-01171 Dresden, Germany.
authors: R
authors: R
authors: Ganesh