Broader Impacts Leon M. Balents, University of California-Santa Barbara, DMR 0804564

1. Definitive Identification of Quantum Spin LiquidsLeon M. Balents, University of California-Santa Barbara, DMR 0804564 A Quantum Spin Liquid (QSL) is a paradoxical state of matter: a magnet without magnetism. In a QSL, electronic magnetic moments, rather than ordering, form a massively entangled quantum superposition state, a kind of macroscopic analog of the famous Einstein-Podolsky-Rosen pair. QSLs have been sought for decades, and are predicted to have many novel properties which may be useful for quantum computation and memory. We showed how entanglement entropy can be used as a smoking gun diagnostic in Density Matrix Renormalization Group calculations for realistic models of magnetism. This proves that QSLs are found in simple and realistic magnetic systems. Calculated entanglement entropy for the kagomé antiferromagnet (top) and phase diagram showing QSL phase in the square lattice J1-J2 model (bottom)

2. Broader ImpactsLeon M. Balents, University of California-Santa Barbara, DMR 0804564 Our group makes a special effort to support education and training of underrepresented groups. One student, SungBin Lee, graduated June 2012, and will begin a postdoc in the fall at U. Toronto. Another, Lucile Savary, gave 4 invited talks at international meetings in the last year. Ru Chen won the best theoretical poster prize at HFM2012. The PI also organized a 4 week program on “Spin orbit physics in correlated electron systems” at the Aspen Center for Physics, as well as serving on numerous other conference and service committees. Group photo of current students and the PI at the excursion for the HFM2012 conference