Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 27: CE: Poster Session

TT 27.81: Poster

Wednesday, March 24, 2010, 14:00–18:00, Poster D1

Vacancies in non-collinear antiferromagnets — •Alexander Wollny, Lars Fritz, and Matthias Vojta — Institut für Theoretische Physik, Universität zu Köln, 50937 Köln, Germany

2D quantum Heisenberg antiferromagnets provide a variety of interesting phenomena. The role of vacancies has been widely studied on the square lattice, e.g. in the context of cuprates, and is reasonably well understood.

For a system with geometrical frustration the situation is more difficult. Here a magnetically ordered state often displays non-collinear order which has a strong influence on the basic excitations of the system, the spin-waves. The simplest realization is the triangular lattice which shows a 120^∘ spin structure. At the classical level, a vacancy induces a local distortion of the spin pattern which partially relieves the frustration.

We perform a classical Monte Carlo simulation which determines the structure of the distortion and shows that it declines exponentially. Thus, it does not correspond to a goldstone mode but can be interpreted as a local condensate of spin-waves. Taken this distortion into account, we study the spin-wave corrections to the classical ground state in linear order and discuss how the vacancy could be seen in a local susceptibility measurement.