Raman response in antiferromagnetic two-leg S=1/2 Heisenberg ladders
Institut für Theoretische Physik, Universität zu
Köln Zülpicher Str. 77, D-50937 Köln, Germany
Accepted: 4 October 2001
The Raman response in the antiferromagnetic 2-leg S=1/2 Heisenberg ladder is calculated for various couplings by continuous unitary transformations. For leg couplings above 80% of the rung coupling a characteristic 2-peak structure occurs with a point of zero intensity within the continuum. Experimental data for and y are analyzed and the coupling constants are determined. Evidence is found that the Heisenberg model is not sufficient to describe cuprate ladders. We argue that a cyclic exchange term is the appropriate extension.
PACS: 75.40.Gb – Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.) / 75.50.Ee – Antiferromagnetics / 75.10.Jm – Quantized spin models
© EDP Sciences, 2001