Three main questions related to the physics of orbital degrees of freedom came to the fore in the discussion of Wednesday (biased view --JvdB).

We know that orbitals can order and that they couple to the lattice, but the questions are:
1. is there any material in which the quantum character of orbital degrees of freedom become relevant?
2. are there any cases where orbital fluctuations, either quantum or classical are relevent?
3. does orbital ordering have interesting textures, symmetries and/or excitations?

Also 15 more or less detailed discussion topics came up:
1. What is the role of vibronic coupling in cooperative Jahn-Teller systems
2. The importance of relativistic spin orbit coupling in eg and t2g systems
3. Orbital and frustration: frustration due to orbital degrees of freedom --- orbitals in frustrated lattices
4. Relative importance of electron-lattice effects (Jahn Teller) versus electronic effects (superexchange).
5. Role of geometry: differences for the situation of 180 degree O-TM-O bonds, 90 degree O-TM-O bonds and edge sharing octahedra
6. Reduced dimensionality due to orbitals
7. Importance of direct d-d electronic hopping versus d-oxygen-d hopping, especially in t2g spinels
8. Orbitals in charge transfer insulators
9. Role of orbital degrees of freedom at metal-insulator transitions
10. Orbital liquids -- quantum effects
11. Orbital waves -- orbitons
12. Importance of long-range interactions in short-range orbital (cooperative Jahn Teller) models
13. Multiplets en Mottiplets
14. Orbital textures, orbital domains and their effect on electronic degrees of freedom
15. What happens to orbital order when going to metallic states --orbital melting

Three main questions related to the physics of orbital degrees of freedom came to the fore in the discussion of Wednesday (biased view --JvdB).

We know that orbitals can order and that they couple to the lattice, but the questions are:

1. is there any material in which the

quantumcharacter of orbital degrees of freedom become relevant?2. are there any cases where orbital

fluctuations, either quantum or classical are relevent?3. does orbital ordering have interesting

textures,symmetriesand/orexcitations?Also 15 more or less detailed discussion topics came up:

1. What is the role of vibronic coupling in cooperative Jahn-Teller systems

2. The importance of relativistic spin orbit coupling in eg and t2g systems

3. Orbital and frustration: frustration due to orbital degrees of freedom --- orbitals in frustrated lattices

4. Relative importance of electron-lattice effects (Jahn Teller) versus electronic effects (superexchange).

5. Role of geometry: differences for the situation of 180 degree O-TM-O bonds, 90 degree O-TM-O bonds and edge sharing octahedra

6. Reduced dimensionality due to orbitals

7. Importance of direct d-d electronic hopping versus d-oxygen-d hopping, especially in t2g spinels

8. Orbitals in charge transfer insulators

9. Role of orbital degrees of freedom at metal-insulator transitions

10. Orbital liquids -- quantum effects

11. Orbital waves -- orbitons

12. Importance of long-range interactions in short-range orbital (cooperative Jahn Teller) models

13. Multiplets en Mottiplets

14. Orbital textures, orbital domains and their effect on electronic degrees of freedom

15. What happens to orbital order when going to metallic states --orbital melting