Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 37: MLT: Poster Session

TT 37.2: Poster

Thursday, March 25, 2010, 14:00–18:00, Poster A

Search for quantum phases in frustrated systems — •Ansgar Kalz, Andreas Honecker, Sebastian Fuchs, and Thomas Pruschke — Institut für Theoretische Physik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen

We use quantum Monte-Carlo simulations to analyse phase diagrams of spin models on two-dimensional lattice geometries with competing interactions. The frustration suppresses the classically ordered phases and we expect the emergence of phases which originate by quantum fluctuations like superfluidity or dimer ordering.

For the square lattice with nearest and next-nearest neighbour interaction the magnetically ordered states are the Néel state and the collinear state. The phase transitions for these classically ordered phases tend towards zero temperature for increasing quantum fluctuations. In a certain region of frustration and quantum fluctuations the classical phases vanish completely and new groundstates appear. We analyse the nature of these new groundstates by calculating correlations of multiple spin interactions.

We present the behaviour of the classical and quantum mechanical order parameters like staggered magnetisation, superfluid density and dimer-dimer correlations in temperature and parameter space. We show finite and zero temperature phase diagrams and look at the properties of the emerging phase transitions.