Schedule Jun 07, 2004
Quantum-criticality in diluted 2D antiferromagnets
Anders Sandvik (Boston University)

Two different 2D Heisenberg S=1/2 antiferromagnets consisting of coupled dimers have been studied using quantum Monte Carlo simulations; a bilayer where a dimer consists of spins in different layers and and a single layer with staggered dimers. Due to the tendency to singlet-formation on the dimers, these models have quantum-critical points as a function of the intra-bilayer coupling. By randomly removing a fraction p of the dimers, quantum-criticality in the presence of disorder can be studied. Here the focus will be on the behavior at the geometrical percolation point, where the spin system on the percolating cluster has a fractal dimensionality d=91/48. The critical coupling at which the percolating cluster becomes quantum-critical is extracted and some critical exponents are calculated as well. It is shown that the critical point is different for the two models, likely due to the layer-exchange symmetry of the bilayer model. The behavior at pecolation for coulings less than the critical coupling is also different. In the bilayer model the dilution-driven transition in this case is a classical percolation transition, whereas the single-layer model exhibits a line of quantum-critical points with continuoulsy varying exponents.

Begin WebCam and audio for the whole talk: high bandwidth or medium bandwidth.
Or, begin audio only for the whole talk: high bandwidth or low bandwidth. (Or, right-click to download the whole audio file.)

Begin QuickTime of the whole talk (high bandwidth).

To begin viewing slides, click on the first slide below. (Or, view as pdf.)

[01] [02] [03] [04] [05] [06] [07] [08] [09] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19]

Author entry (protected)