BEGIN:VCALENDAR VERSION:2.0 PRODID:Data::ICal 0.22 BEGIN:VEVENT DESCRIPTION:Oleg Tchernyshyov\, Johns Hopkins University\n\nA spin liquid i s a hypothetical quantum ground state of a frustrated Heisenberg magnet co njectured by P.W. Anderson in the 1970s. Its distinguishing features are ( 1) a lack of magnetic order and (2) a degeneracy that depends on the topol ogy of the system. The status of spin liquids has been recently upgraded f rom purely speculative to plausible as these ground states were found in r elatively simple two-dimensional spin models on square and kagome lattices . Experiments with herbertsmithite yielded clues of spin excitations with fractional spin 1/2 in a kagome antiferromagnet.\n
\nI will present a ph enomenological Z_2 lattice gauge theory that describes low-energy properti es of the spin liquid in a S=1/2 Heisenberg antiferromagnet on kagome. It reproduces many of the characteristic features observed in recent numerica l studies of the model\, including the ground-state degeneracy\, response to quenched disorder\, and spinon states near the system's edge. DTSTART:20130418T193000Z LOCATION:Physics Building\, Room 204 SUMMARY:Z_2 spin liquid in the Heisenberg antiferromagnet on kagome END:VEVENT END:VCALENDAR