Mesoscopic Quantum Critical Regimes and Disorder-Driven Deconfinement

Grants and Contracts Details


~~ During the past decade the interplay of quenched disorder and electronic interactions has emerged as one of the most interesting and challenging areas in condensed matter phy-sics. The focus of this proposal is systems in which disorder and interactions conspire to create novel states with strong quantum fluctuations. In bulk systems strong quantum fluctuations are characteristic of the quantum critical regime near the bulk quantum phase transition. In mesoscopic systems the PI's past work shows that single-particle perturbations which move the system from one Random Matrix symmetry class to another also enhance quantum fluctuations of corresponding physical quantities. Such strongly fluctuating mesoscopic systems are fascinating because they are universal many-body extentions of Random 11atrix crossover ensembles, open a zero-dimensional window on bulk quantum criticality, and are easily manipulated experimentally. The PI's past work offers a method to study such regimes nonperturbatively in both disorder and interactions. Also of fundamental interest is the manner in which the mesoscopic system approaches the bulk limit near a quantum phase transition. The key focus will be to understand how quantum critical physics is manifested in transport. The successful completion of this research will make it possible to create, control, and characterize mesoscopic systems with strong quantum fluctuations. Recently, tremendous progress has recently been made in identifying deconfined phases and critical points in two-dimensional quantum antiferromagnets. While such deconfined regimes are difficult to access in realistic lattice spin systems, and are probably unstable to quenched disorder, the PI has noticed that deconfinement is generically possible in disordered multicomponent quantum Hall systems, and is in fact driven by quenched disorder. The fundamental reason is the spin-charge relation of the lowest Landau level, which forbids hedgehogs/monopoles by local charge conservation. In turn, the suppression of these topological objects leads to deconfinement. Smooth disorder is needed to restore the broken symmetry of the quantum Hall ferromagnet and push the system into a deconfined state. The v = 1 bilayer system, which experimentally shows dissipation at the lowest .measured temperatures, is a good candidate for such a deconfined state. The successful completion of this research will result in a deeper understanding of both deconfined phases and multi component quantum Hall systems. Broader impact: The education· of a postdoc and a graduate student in the latest techniques of mesoscopic and strongly correlated physics is an integral part of this proposal. In collaboration with J.·P. Eisenstein, H. A. Fertig, and Z. Wang, the PI is organizing a conference on disorder in condensates in the Spring of 2008 to bring together researchers and pool ideas about treating disorder and interactions in diverse subfields. Finally, the PI plans to produce a website of Jackson-level problems in Electrodynamics, with solutions available to instructors upon request. 1
Effective start/end date12/15/0711/30/11


  • National Science Foundation: $300,000.00


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