Condensed Matter Seminar Announcement Prof. Ashvin Vishwanath UC Berkeley " Landau Forbidden Transitions and Deconfined Quantum Criticality " Date: Thursday, April 7, 2005 416 Phy/Geo Time: 4:10 pm. Abstract: Our modern understanding of phase transitions is built on Landau's theory, which, among other things, dictates when it may be possible to have a continuous transition between two phases. For example, a continuous transition between two phases with unrelated orders is forbidden in this theory without special fine tuning. In this talk I will argue that in the case of quantum phase transition, precisely such `Landau forbidden' phase transition may occur. In particular, a theory for a direct continuous transition between the Neel and VBS phases of a two dimensional quantum magnet will be presented. This critical theory is naturally described in terms of fractionalized excitations (spinons) and a conserved flux that only emerges at the transition. In contrast the two phases involved, the Neel and VBS are both conventional phases. Recent extensions of this theory to other transitions and possible relevance to phenomena in strongly correlated materials will be discussed.

E-Mail: ashvinv@socrates.berkeley.edu
Web Page: http://www.berkeley.edu/