Seminar Lecture

Speaker : Dr. Subroto Mukerjee
Materials Science Division
Lawrence Berkeley National Laboratory, Berkeley CA
Topic : Spinor condensates: Phase transitions, vortex lattices and dynamics
Date : December 20, 2007
Time : 12.00 noon
Venue : C V Raman Hall, IACS

All are cordially invited to attend.

Abstract: Spinor condensates (condensates of atoms with non-zero spin) have been the subject of intense theoretical and experimental investigation in the last 10 years. The spin degree of freedom allows for spin ordering in addition to superfluid order causing these systems to have interesting phases and phase transitions. I will show that some of these phases are analogous to those encountered in liquid crystals. The topological defects of these phases combine spin and charge and lead to interesting effects. I will show that in a 2D system with antiferromagnetic spin-spin interactions, these defects drive a Kosterlitz-Thouless transition to a "nematic superfulid" phase. Like in a regular superfluid, toplogical defects in a spinor condensate also form a lattice under rotation. However, the combination of spin and charge produces lattices more exotic than the triangular lattice obtained in a regular superfluid. In particular, I will demonstrate that it is possible to cause transitions between different types of lattices (including one to a quasi-periodic structure) by tuning the temperature and magnetic energy. Finally, using the dynamic critical exponent as a diagnostic tool, I will describe the magnetic coarsening dynamics of spinor condensates in terms of various dynamical models incorporating different possible conservation laws. The conservation laws besides the one for magnetism will be shown to have an insignificant effect on the coarsening.