Physics & Astronomy Colloquium
3:30 PM, Friday, October 16, 2009
Room 155, Chem-Phys Building
Dr. Alex Seidel
Department of Physics
Washington University, St. Louis
"The bare essentials of topological orders in fractional quantum
Hall liquids''
Condensed matter physicists are generally faced with the task of
solving problems involving some 1024 particles that interact
strongly. Amazingly, in many cases this task of seemingly hopeless
complexity is amenable to the following simple strategy: Try to find a
way to (almost) switch off the interactions in a manner that preserves
all the fundamental properties of the system. If this is possible, one
says that the system is ``adiabatically connected'' to a non-interacting
system.
In the past 20+ years, however, much focus has been on problems where
the traditional approach does not seem feasible. In particular, a new
paradigm has surfaced which applies to certain novel incompressible
quantum liquids that are said to have ``topological order''. This new
paradigm encompasses the fractional quantum Hall liquids, and possibly
states that can be realized in quantum magnets.
The phenomenology of topologically ordered states is very exotic,
including fractionally charged excitations and anyonic braiding
statistics. This fact seems to preclude the possibility that these
states have simple non-interacting limits. In spite of this, it will
be shown in this talk that such a trivial limit does exist for
fractional quantum Hall liquids. In this limit, a simple language of
one-dimensional patterns emerges. I will show how this language
efficiently encodes the defining quantum numbers of the underlying
quantum Hall state, such as fractional charges, characteristic
degeneracies, and even non-abelian braiding statistics.
Refreshments will be served in CP 179 at 3:15 PM |
