Ordering near the percolation threshold in models of two-dimensional interacting bosons with quenched dilution

Bray-Ali, N and Moore, JE and Senthil, T and Vishwanath, A (2006) Ordering near the percolation threshold in models of two-dimensional interacting bosons with quenched dilution. In: Physical Review B, 73 (6). 064417-1.

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Abstract

Randomly diluted quantum boson and spin models in two dimensions combine the physics of classical percolation with the well-known dimensionality dependence of ordering in quantum lattice models. This combination is rather subtle for models that order in two dimensions but have no true order in one dimension, as the percolation cluster near threshold is a fractal of dimension between 1 and 2: two experimentally relevant examples are the O(2) quantum rotor and the Heisenberg antiferromagnet. We study two analytic descriptions of the O(2) quantum rotor near the percolation threshold. First a spin-wave expansion is shown to predict long-ranged order, but there are statistically rare points on the cluster that violate the standard assumptions of spin-wave theory. A real-space renormalization group (RSRG) approach is then used to understand how these rare points modify ordering of the O(2) rotor. A new class of fixed points of the RSRG equations for disordered one-dimensional bosons is identified and shown to support the existence of long-range order on the percolation backbone in two dimensions. These results are relevant to experiments on bosons in optical lattices and superconducting arrays, and also (qualitatively) for the diluted Heisenberg antiferromagnet La-2(Zn,Mg)(x)Cu1-xO4.

Item Type:	Journal Article
Publication:	Physical Review B
Publisher:	American Physical Society
Additional Information:	Copyright of this article belongs to American Physical Society.
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	16 Sep 2010 05:31
Last Modified:	19 Sep 2010 06:15
URI:	http://eprints.iisc.ac.in/id/eprint/31759

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