Spin-orbit interaction in the fcc lattice with application to ordered double perovskites

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Date/Time:Thursday, 06 May 2010 from 4:10 pm to 5:00 pm
Location:Physics 5
Phone:515-294-0849
Channel:Condensed Matter Physics
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Rodrigo Pereira, The Kavli Institute for Theoretical Physics, University of California Santa Barbara

Heavy-atom based ordered double perovskites constitute a playground for strong spin-orbit physics in transition metal oxides. Recent experiments have revealed that isostructural compounds can show rather disparate magnetic properties, ranging from weak ferromagnetism to, apparently, spin liquid behavior. In this talk I will present a model for the spin and orbital interactions in cubic double perovskites that are Mott insulators with one electron occupying a triply degenerate (t2g) orbital. I will describe two stable ground states for the effective model: one ordered state with multipolar order but reduced magnetic moment (a "hidden order" state) and one disordered state in which four flavors of spinons form a Fermi surface (a "spin-orbital liquid" state). I will also discuss the connection with experimental results.