Regensburg 2000 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 21: Korrelierte Elektronen II

TT 21.3: Vortrag

Donnerstag, 30. März 2000, 15:15–15:30, H18

Flow equations and new weak-coupling solution for the spin-polaron in a quantum antiferromagnet — •Jürgen Stein — Institut für Theoretische Physik, Ruprecht-Karls-Universität Heidelberg, Philosophenweg 19, 69120 Heidelberg

The t-J model for the doped two-dimensional Heisenberg quantum antiferromagnet is studied in the generalized Dyson-Maleev representation, applying a new continuous unitary transformation which eliminates the coupling of spin and charge degrees of freedom. The analytical solutions of the resulting flow equations are derived in the weak-coupling regime where t/J is small. This continuous transformation yields a new weak-coupling result for the dispersion of the spin-polaron, if the elimination of both the nondiagonal spin-wave contributions and the terms coupling holes and spin-waves is performed simultaneously. The associated one-particle ground state is lower in energy than the corresponding perturbative result, which is reproduced upon application of subsequent transformations.