Dresden 2011 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 44: Poster Session Correlated Electrons
TT 44.63: Poster
Thursday, March 17, 2011, 10:00–13:00, P1
Finite-size scaling analysis of the frustrated square-lattice Heisenberg model — •Burkhard Schmidt, Mohammad Siahatgar, and Peter Thalmeier — Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden
The two-dimensional frustrated next nearest neighbor Heisenberg model on the square lattice is a prime example for a spin system where quantum fluctuations can either destroy or stabilize magnetic order. The phase boundaries and staggered moment dependence on the frustration ratio J2/J1 of the exchange constants are fairly well understood both from approximate analytical and numerical methods. We use exact diagonalization for finite clusters for an extensive investigation of the more general J1a,b-J2 model to clarify the dependence of ground-state energy and ordered moment on exchange frustration and anisotropy. Exact diagonalization is an unbiased approach, however it is restricted to small tiles, and we have to account for finite-size effects. We therefore introduce a systematic way of uniquely generating all possible tilings of the square lattice, define a compactness parameter for selecting the tiles to be included into the scaling procedure and, for this low symmetry model, define a controlled procedure for the finite size scaling that is compatible with the possible magnetic phases. We apply the scaling procedure to the ground-state energy, the static structure factor, and the static long-distance correlation function of the J1a,b-J2 model at different characteristic points in the parameter space of the Hamiltonian. The tile size dependence of the ordered moment is derived from the latter two quantities.