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TT: Fachverband Tiefe Temperaturen

TT 10: Correlated Electrons: (General) Theory 1

TT 10.2: Vortrag

Montag, 26. März 2012, 15:15–15:30, H 3010

Spectral properties of one-dimensional spin systems using deepCUT — •N. A. Drescher, H. Krull, T. Fischer, and G. S. Uhrig — TU Dortmund, Theoretical Physics I, 44221 Dortmund

Directly evaluated enhanced perturbative continuous unitary transformations (deepCUT) are a novel scheme to systematically derive effective low-energy models for many-particle Hamiltonians. Founded on high-order perturbative expansion techniques (epCUT), deepCUTs generate robust results beyond perturbation theory. We use them to decouple ground state and low-lying excitations of one dimensional spin systems. From the effective Hamiltonian, dispersion and bound states can be obtained. Applying the same unitary transformation to observables, we calculate spectral weights and the dynamical spin structure factor for the one and two quasi-particle channel at T=0.

We illustrate the deepCUT method by an analysis of the antiferromagnetic S=1/2 Heisenberg ladder compound (C₇ (D,H)₁₀ N)₂ CuBr₄. We compare our results for dispersion and spectral weight with inelastic neutron scattering data. Predictions for S=0,1 spectral densities and bound states relevant for various scattering experiments are presented.