Berlin 2008 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 1: Critical phenomena and phase transitions

DY 1.3: Vortrag

Montag, 25. Februar 2008, 10:45–11:00, MA 004

Spin-1/2 XX chain with three-site interactions: Dynamic properties — •Joachim Stolze¹, Oleg Derzhko², Taras Krokhmalskii², and Taras Verkholyak² — ¹Institut für Physik, TU Dortmund, Germany — ²Institute for Condensed Matter Physics, L'viv, Ukraine

We consider a spin-1/2 XX chain in a transverse (z) field with (XZX+YZY)-type three-site interactions. After performing the Jordan-Wigner transformation to spinless fermions, these interactions induce only a (real) next-nearest-neighbor hopping of spinless fermions preserving the exact solvability of the problem. We focus on dynamic properties of the model in its various ground-state phases. We report a closed-form expression for the zz dynamic structure factor and for some other dynamic structure factors all of which are governed by a two-fermion (particle-hole) excitation continuum. We examine the properties of the two-fermion excitation continuum (boundaries, soft modes, van Hove singularities). The xx dynamic structure factor is governed by many-fermion excitations. We report both analytical (in the high-temperature limit and in the zero-temperature strong-field regime) and numerical results for this dynamic structure factor. Throughout our study we discuss in some detail those features of the dynamic structure factors which indicate the presence of the three-site interactions.

This research was supported by a NATO collaborative linkage grant (CBP.NUKR.CLG 982540, project "Dynamic Probes of Low-Dimensional Quantum Magnets").