The
Centre for Mathematical
Physics
SEMINAR
Speaker: Jon Links, CMP - UQ
Title:
Zeroth order quantum phase transition in the BCS model with p+ip pairing
10am,
Thursday 31st July, 2008
Abstract:
Cooper pairing with p-wave symmetry is believed to underlie the superfluidity of helium 3 and the superconductivity of
strontium ruthenate, as well as being relevant to
current experiments with cold fermi gases. In 2000
Read and Green conducted a mean-field analysis of the BCS Hamiltonian with p+ip pairing and argued the existence of a topological
quantum phase transition. In the strong phase the ground-state wavefunction exhibits tightly bound Cooper pairs, while in the
weak phase the wavefunction is asymptotically the
Moore-Read Pfaffian fractional quantum
Hall state. The Moore-Read state, which has its origins in conformal
field theory, is widely studied as a trial state to describe non-abelian topological phases.
In this talk I will first review the mean-field studies of Read and Green.
Then I will discuss an alternative analysis of the p+ip
model using the exact Bethe ansatz solution. The two
main results I will present are 1) there is a curve in the phase diagram,
parameterised by the coupling and the filling fraction, for which the ground
state is exactly the Moore-Read state; 2) this curve corresponds to a zeroth order quantum phase transition, which simply means
the ground state energy is discontinuous in the thermodynamic limit.
This is joint work with M. Ibanez, G. Sierra (
All interested are invited to attend.
Enquiries to Katrina Hibberd
email: keh@maths.uq.edu.au