Date/Time
Date(s) - 14/02/2005
3:30 pm - 4:30 pm

Title: Superfluid-Insulator Transition in Two-Dimensional Superfluids

Speaker: Dr. Anton Burkov

Institute: University of California, Santo Barbara

Location: ABB 165

Description:

I will discuss the recently developed theory of a direct superfluid to Mott insulator transition in two-dimensional (2D) lattice bosonic systems. The central concept in this theory is the concept of boson-vortex duality. Under this duality, the problem of bosons on a lattice translates into the problem of vortices, moving in a fluctuating “magnetic” flux, that is proportional to the boson density. Superfluid-insulator transition in the original bosonic system can then be described as Bose condensation of vortices in the minima of the vortex Hofstadter spectrum. These minima transform under a projective representation of the spatial group of the lattice, which means that vortex condensation is generally accompanied by a broken lattice symmetry. This allows to naturally describe insulating ground states with broken spatial symmetries. Thus, unlike in the traditional Landau-Ginzburg-Wilson theory of phase transitions, both phases are characterized in this description by a single vortex field, which leads to a generic possibility of a direct second order transition between them. I will discuss the general properties of the superfluid to Mott insulator transition for bosons on the square and triangular lattices, implied by this theory, and comment on the experimental relevance of these results.