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TT: Fachverband Tiefe Temperaturen

TT 33: Postersession Correlated Electrons: Metal Insulator Transition, Spin Systems and Itinerant Magnets

TT 33.18: Poster

Mittwoch, 25. März 2009, 14:00–18:00, P1A

Effective Hamiltonians for Doped Spin-1/2 Ladders from Self-Similar Continuous Unitary Transformations — •Sebastian Duffe, Tim Fischer, and Götz S. Uhrig — Technische Universität Dortmund

Doped spin-1/2 ladder systems are important model systems for 2D high-T_C superconductors. Their one-dimensionality renders them more tractable to various analytic and numerical approaches. Experimentally such ladder systems are realized in the so-called telephone number compounds Sr,Ca,La₁₄Cu₂₄O₄₁.
Here we systematically derive effective Hamiltonians for the hole motion in such spin ladders. The technique of choice are continuous unitary transformations (CUTs) which are performed self-similarly for the coefficients of operator monomials in real space in second quantization. The proliferating number of terms is bounded by truncating far reaching processes which reach longer than the finite correlation length. The magnetic excitations are triplons on the rungs of the ladder; the charge excitations are holes with spin living also on the rungs of the ladder. The effective Hamiltonian allows us to read off the dispersions of single excitations directly. But it also contains their interaction.