Berlin 2015 – wissenschaftliches Programm
TT 71.29: Poster
Mittwoch, 18. März 2015, 15:00–18:00, Poster B
Optical absorption of the spin-1/2 Heisenberg antiferromagnet on a triangular lattice — •Boris Celan and Wolfram Brenig — Institute for Theoretical Physics, Technische Universität Braunschweig
We investigate the optical absorption of the spin-1/2 antiferromagnetic Heisenberg model on the two-dimensional anisotropic triangular lattice.
Vertex functions for the absorption of light are derived within a model of phonon-assisted multimagnon excitations and their momentum dependence is analyzed. For the magnetic excitations we use linear spin-wave theory. For the optical conductivity we derive a Bethe-Salpeter equation including quasi-particle renormalization and irreducible vertex functions to order 1/S. Numerical solutions of this integral equation are discussed on finite lattices up to 33x33 sites with and without final-state interactions.
We find the optical absorption to be qualitatively insensitive to the inclusion of final-state interactions. Results will also be presented for optical vs acoustic phonons. For low frequencies we derive asymptotic analytic expressions for the absorption which will be compared to our numerical results.