Dresden 2003 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 2: Systeme korrelierter Elektronen I

TT 2.5: Vortrag

Montag, 24. März 2003, 11:00–11:15, HSZ304

Theoretical analysis of magnetic Raman scattering in La2CuO4: two-magnon intensity with the inclusion of ring exchange — •Andrey Katanin^1,2 and Arno P, Kampf¹ — ¹Theoretische Physik III, EKM, Institut fuer Physik, Universitaet Augsburg — ²Institute of Metal Physics, 620219, Ekaterinburg, Russia

We evaluate the Raman light scattering intensity for the square lattice Heisenberg antiferromagnet with plaquette ring exchange J. With the exchange couplings as fixed before from an accurate fit to the spin-wave dispersion in La2CuO4, leading in particular to J=0.24J, we demonstrate in a parameter free calculation that the inclusion of the plaquette exchange contribution to the dispersion and the magnon-magnon interaction vertex gives a peak position in B_1g scattering geometry E_max = 2.71J which is in excellent agreement with the experimental data. Yet, the intrinsic width and the lineshape of the two-magnon remain beyond a descriptions in terms of a spin-only Hamiltonian.