BEGIN:VCALENDAR VERSION:2.0 CALSCALE:GREGORIAN PRODID:UW-Madison-Physics-Events BEGIN:VEVENT SEQUENCE:0 UID:UW-Physics-Event-3301 DTSTART:20140428T213000Z DURATION:PT1H0M0S DTSTAMP:20260419T193321Z LAST-MODIFIED:20140425T125736Z LOCATION:Chamberlin 5310 SUMMARY:"Coupled electricity and magnetism in Mott insulators: current s\, dipoles and monopoles\, Condensed Matter Theory Group Seminar\, Da niel Khomskii \, University of Cologne\, Germany DESCRIPTION:The standard point of view is that at low energies Mott in sulators exhibit only magnetic properties\, while charge degrees of fr eedom are frozen out\, because electrons are localized. I demonstrate that in general this is not true [1\, 2]: for certain spin textures th ere exist quite nontrivial effects in the ground and lowest excited st ates\, connected with charge degrees of freedom. In particular this ma y happen in frustrated systems\, e.g. containing triangles or tetrahed ra as building blocks. I will show that in some cases there may exist spontaneous circular currents in the ground state of insulators\, prop ortional to the scalar chirality\; this clarifies the meaning of the l atter and opens the ways to directly experimentally access it. For oth er spin structures there may exist spontaneous charge redistribution\, so that average charge at a site may be different from 1. This can le ad to the appearance of dipole moments and possibly of the net spontan eous polarization. This is a novel\, purely electronic mechanism of mu ltiferroic behaviour. In particular I show [3] that such electric dipo les should exist in spin ice materials at every tetrahedra with three -in/one-out or one-in /three-out spin configurations\, which are equiv alent to magnetic monopoles [4]. Thus there should be an electric dipo le attached to each magnetic monopole in spin ice. This leads to elect ric activity of magnetic monopoles\, and opens the possibility to con trol magnetic monopoles by electric field. I will also discuss unconve ntional dynamics of magnetoelectric materials\, in which there should be magnetic monopole attached to each electric charge [5]. The possibi lity to use chirality as qubits will be also discussed. \n [1] L.N.Bul aevskii\, C.D.Batista\, M.V.Mostovoy and D.I.Khomskii\, Phys.Rev.B 78 \, 028402 (2008) \n[2] D.I.Khomskii\, JPCM 22\, 164209 (2010) \n[3] D.I.Khomskii\, Nature Communications 3\, Article 904 (2012) \n[4] C. Castelnovo\, R.Moessner and S.L.Sondhi\, Nature 451\, 42 (2008) \n[5] D.I.Khomskii\, arXiv:1307.2327 (2013) \n URL:https://www.physics.wisc.edu/events/?id=3301 END:VEVENT END:VCALENDAR