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MA: Magnetismus

MA 13: Poster:Schichten(1-23),Spinabh.Trsp(24-41),Exch.Bias(42-56),Spindyn.(57-67),Mikromag.(68-76),Partikel(77-90),Spinelektr.(91-97),Elektr.Theo.(98-99),Mikromag+PhasÜ+Aniso.(100-105),Magn.Mat.(106-118),Messmethod.(119-121),Obflm.+Abbverf.(122-123)

MA 13.57: Poster

Dienstag, 9. März 2004, 15:00–19:00, Bereich A

Transition rates via Bethe ansatz for the XXZ and the XX chain — •Daniel Biegel¹, Michael Karbach^1,2, Gerhard Müller², and Klaus Wiele¹ — ¹Bergische Universität Wuppertal, Fachbereich Mathematik und Naturwissenschaften, Physik, 42097 Wuppertal — ²Department of Physics, University of Rhode Island, Kingston, RI 02881-0817, USA

As part of a study that investigates the dynamics of the s=1/2 XXZ model in the planar regime |Δ| < 1, we discuss the singular nature of the Bethe ansatz equations for the case Δ = 0, i.e. the XX model. We identify the general structure of the Bethe ansatz solutions for the entire XX spectrum, which include states with real and complex magnon momentas. We present determinantal expressions for transition rates of spin fluctuation operators between Bethe wave functions. As an application, we calculate lineshapes for dynamic structure factors relevant for experiments. The predominant excitations are identified within the framework of quasiparticles excited from a corresponding vacuum.