Course Coordinator: 
Yejun Feng
Condensed Matter Physics

Condensed matter physics is both old fashioned (originated from solid state physics in 1950’s or even metal physics in 1920’s) and also new style (with emphasis on collective behaviour, symmetry, and topological conditions). Over the past century, this sub-field of physics has grown into a monstrous size with various ramifications such that any offered perspective would always be partial and biased. Here this class will be served at the introduction level, and at a few places, I will try to demonstrate how to evolve from fundamental concepts to perspectives of advanced topics. Nevertheless, the first half of this course is built on the single particle picture and is of mean field nature. The second half starts to introduce a few examples of electron correlation. More specialized fields, such as spintronics and topological states and excitations, will not be covered here. 

This is a class designed for beginner students who would pursue a Ph.D. in fields related to physics, materials science, device engineering, and chemistry. The course covers major concepts and topics in condensed matter, with an emphasis on the shifting new perspective and paradigms in this evolving field. During the weekly three-hour lecture, I will try to split the time with half on theory and half on experimental demonstration of those theoretical concepts.
Course Content: 
  1. Introduction: the change of perspective and paradigms.
  2. Crystals and Symmetry.
  3. Phonons.
  4. Inelastic probes.
  5. Order and disorder
  6. Phase transitions and Landau’s theory
  7. Band structure
  8. Fermi surface probes.
  9. Hatree-Fock.
  10. Electronic excitations in metals.
  11. Electrical transport.
  12. Superconductivity: BCS.
  13. Superconductivity: Quasi-particle gap.
  14. Superconductivity: GL.
  15. Josephson tunnelling.
  16. Josephson devices.
  17. Parity sensitive probes.
  18. Odd parity superconductivity.  
  19. Magnetic interactions
  20. Itinerant magnetism
  21. Spin glass and spin ice
  22. Spin excitations and spin liquids.
  23. Quantum phase transitions.
  24. Non-conventional quantum phase transition.

Notes on Assessement:

There will be four to six assignments. For each assignment, each student is expected to pick one original research paper out of 3-5 suggested choices, and write an essay on it. Each essay should represent individual’s own work and should not be the collective effort of a study group. The writing format could be either a critique of the research paper (~1000 words) either placed in its contemporary context or from a historical retrospect, or detailed mathematical derivations of certain formula. For the final presentation, each student is expected to give a half-hour presentation to extensively discuss one of his/her homework assignment papers in a perspective of both depth and breadth, much beyond his/her homework scope.

Course Type: 
Essays (4-6) 70%, final presentation, 30%.
Text Book: 
Ashcroft & Mermin, Solid State Physics (1967).
Chaikin & Lubensky, Principles of condensed matter physics (1995).
Reference Book: 
D. Pines, Elementary excitations in solids (1963).
L. P. Levy, Magnetism and superconductivity (1997).
J. R. Schrieffer, Theory of superconductivity (1964).
S.K. Ma, Modern theory of critical phenomena (1976).
M Tinkham, Introduction to superconductivity (1996).
Prior Knowledge: 

Students are required to have basic understanding of quantum mechanics (e.g., A216 QM I and A217 QM II), and basic concepts of statistics.