1. Quantum complexity in condensed matter physics
S Julian
University of Toronto
Emergent properties
Particle behaviour of fluctuating modes
Broken symmetry and rigidity
Indirect interaction

2. Condensed Matter Physics
Fundamental Physics
Applied Physics
-Quantum properties of many body systems
-Noise (eg in electronic circuits)
-Novel soft matter, elasticity and viscosity
-Modeling the universe
-memory devices for computers
-processors for computers
-corrosion and catalysis
-superconducting devices
Elementary particle physics
energy
Condensed matter physics
biology
time

3. Combinatorial chemistry vs. emergent properties

4. Empty boxes are more interesting than people think!
At 0K: zero point motion
At high T: electrons and
positrons are created
At Low T: black-body radiation

5. Analogy with quantum condensed matter physics:
At 0K: zero point motion
of phonon, electron-hole pairs, etc.
At high T: electrons and
positrons are created
At Low T: black-body radiation
Real phonons and electrons+holes

6. Dispersion relations for (quasi)particles

7. How to make a metal

8. Conventional phase transition: broken symmetry states

9. Conventional phase transition
Spontaneous symmetry breaking
The susceptibility diverges
> rigidity

10. Mass enhancement
Magnetic pairing

11. Indirect interactions:
- One of the central principles of physics

12. Unusual “particle-like” excitations are possible in condensed matter systems
Overdamped modes
Propagating modes

13. The quantum critical pointFe Cu
At Tc, fluctuations diverge

14. quantum critical superconductivity?

15. CePd2Si2 phase diagram

16. Methodology of condensed matter physics:
Crystal growth:
Crystals are to us what stars are to astronomers
Scattering:
A good way to find out what is inside something is to throw something at it and see how it bounces off
Nano-physics:
Scanning tunneling microscopy, point contact spectroscopy, etc.
Low temperatures and high magnetic fields:
Dilution refrigeration

17. Anvil pressure cells

18. Antiferromagetic insulator
Phase diagram of Ca2RuO4
Antiferromagetic insulator
Temperature / K
Ferromagnetic metal
Pressure / kbar

19. Structural transitions

20. Atomic orbitals in crystals

21. Orbital ordering

22. Summary
The fundamental principles of quantum condensed matter physics are:
Emergent properties: new kinds of ‘particles’ emerge as complexity increases
Broken symmetry and rigidity
Indirect interactions
The methodology focuses on crystal growth, scattering and low temperatures.