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TT: Fachverband Tiefe Temperaturen

TT 49: CE: Spin Systems and Itinerant Magnets 2

TT 49.7: Vortrag

Donnerstag, 17. März 2011, 15:45–16:00, HSZ 03

Series Expansion Analysis of a Four-Spin Tube — Marcelo Arlego¹ and •Wolfram Brenig² — ¹Departamento de Física, Universidad Nacional de La Plata, 1900 La Plata, Argentina — ²Institute for Theoretical Physics, Technische Universität Braunschweig, 38106 Braunschweig, Germany

We analyze a four-legged anisotropic triangular spin ladder with transverse periodic boundary conditions leading to a frustrated four-spin tube. In the limit of strong rung coupling, and starting from decoupled four-spin plaquettes, we study the zero temperature properties of this quantum spin model, using a series expansion based on the flow equation method. Results will be reported for the ground state energy, as well as for the dispersion of the one- and the two-particle excitations. The effective two-particle interactions will be analyzed and are shown to induce several types of (anti)bound states. In sharp contrast to conventional spin ladders, the renormalized plaquette regime of the four-spin tube is unstable to quantum-phase transitions at finite leg couplings. These are reported to be of first order and their critical lines will be determined using the density-matrix renormalization group.