Physics Colloquium, October 22, 2002

What happens when Topology, Quantum Mechanics and Superconductivity meet?

Carlos Sa de Melo

Georgia Tech

Answer: A topological quantum phase transition, but only in unconventional (non-s-wave) superconductors.

Standard classical phase transitions (which occur at finite temperatures) and standard quantum phase transitions (which occur at zero temperature) always involve a change in symmetry. The appearance of an order parameter for the ordered phase indicates this symmetry change. However, topological quantum phase transitions do not involve a change in symmetry, but involve a change in the topology of the ground state (T = 0). The particular case of a d-wave superconductor with varying charge carrier concentration will be discussed as an example of a topological quantum phase transition.

3.30 p.m., Smith Laboratory, Room 1005

Refreshments served in Smith 1094 at 3:00 p.m.