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Unconventional Bose-Einstein condensation beyond the no-node paradigm

Speaker: Congjun Wu University of California, San Diego
Time: 2011-07-19 10:00-2011-07-19 11:00
Venue: FIT 1-222


Feynman's "no-node" theorem states that the conventional many-body ground state wavefunctions of bosons in the coordinate representation are positive de nite. This implies that time-reversal symmetry cannot be spontaneously broken. In this talk, we present our progress in studying a class of new states of unconventional Bose{Einstein condensations beyond this paradigm. These states can either be the long-lived metastable states of ultracold bosons in high orbital bands in optical lattices as a result of the "orbital Hund's rule" interaction, or the ground states of spinful bosons with spin-orbit coupling linearly dependent on momentum. In both cases, Feynman's argument does not apply. The resultant many-body wavefunctions are complex-valued and thus break time-reversal symmetry spontaneously. Exotic phenomena in these states include the Bose-Einstein condensation with on-site orbital angular momentum, the half-quantum vortex, and the spin texture of skyrmions.

Short Bio:

Congjun Wu received his B. S. in Physics from Tsinghua University in 1997, M. S. in Physics from Peking University in 2000, and his Ph.D. in physics from Stanford University in 2005. He did his postdoctoral research at the Kavli Institute for Theoretical Physics, University of California, Santa Barbara, from 2005 to 2007. He became an assistant professor in 2007, and
an associate professor in 2011 in the Department of Physics at the University of California, San Diego. His research interests include quantum magnetism, superconductivity, orbital physics, and topological states in condensed-matter and cold-atom systems.