Regensburg 2002 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 13: Systeme korrelierter Elektronen: Theorie I

TT 13.3: Vortrag

Dienstag, 12. März 2002, 15:15–15:30, H20

Spin Excitations in La2CuO4: Consistent Description by Inclusion of Ring Exchange — •Andrey Katanin^1,2 and Arno Kampf¹ — ¹Institute fur Physik, Theoretische Physik III, Universitat Augsburg, 86135 Augsburg, Germany — ²Institute of Metal Physics, Kovalevskaya st. 18, 620219, Ekaterinburg, Russia

We consider the square lattice Heisenberg antiferromagnet with plaquette ring exchange and a finite interlayer coupling leading to a consistent description of the spin-wave excitation spectrum in La₂CuO₄. The values of the in-plane exchange parameters, including ring-exchange J, are obtained consistently by an accurate fit to the experimentally observed in-plane spin-wave dispersion, while the out-of-plane exchange interaction is found from the temperature dependence of the sublattice magnetization at low temperatures. The fitted exchange interactions J=151.9meV and J=0.24J give values for the spin stiffness and the Néel temperature in excellent agreement with the experimental data.