Condensed Matter Seminar Series

Title: Ordering Near Percolation Threshold in Models of Interacting Bosons with Quenched Dilution

Noah Bray-Ali

University of California at Berkeley

Monday March 6,  10:00 am,  Room 298,  Physics Building

Abstract: Randomly diluted quantum boson and spin models in two dimensions combine the physics of classical percolation with the dimensionality dependence of ordering in quantum models. This combination is rather subtle for the percolation cluster near threshold, because it has fractal dimension between one and two. Two experimentally relevant examples are quantum rotors and Heisenberg antiferromagnets. This seminar follows two related approaches to quantum rotors. In the first, we expand away from the classical phase and see that it is stable to small fluctuations. In the second, we focus on the quantum rotors living on a certain, quasi-one-dimensional sub-lattice of the percolation cluster, and see that the simple geometry allows us to make asymptotically exact statements even if the rotors fluctuate strongly. The talk closes with some comments on recent numerical and experimental evidence that magnetic order persists at percolation threshold in a quantum antiferromagnet.