Quasiperiodicity, quenched disorder and quantum fluctuations in two dimensional antiferromagnets

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Date/Time:Thursday, 11 Nov 2010 from 4:10 pm to 5:00 pm
Location:Phhys Room 5
Channel:Condensed Matter Physics
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Dr. Anuradha Jagannathan Laboratoire de Physique des Solides Bât.510, Université Paris-Sud 91400 Orsay France

The Heisenberg antiferromagnetic model for quantum spins has been extensively studied, particularly in low dimensions where quantum fluctuations are important. Applications of the model abound in condensed matter physics, the high temperature superconducting parent compounds being only one example. I will begin with a review of some standard 2D antiferromagnets before going on to some new examples of disordered and frustrated models. The complex spatial order present in quasicrystalline thin films will be described, and I will show how this type of structure can give rise to a novel antiferromagnetic ground state, with long ranged excitations of a very different kind from the magnons well-known from periodic systems. Finally I discuss the influence of geometric disorder, and its effect on the propagation of modes and on the antiferromagnetically ordered state, along with possible experimental realizations of such models.