Additional Questions

1.

If we agree that a pseudogap is signaled by the disappearance of portions of the Fermi surface in ARPES (and signatures in other probes but not necessarily all probes), do we agree that there are three broad classes of mechanism for the appearance of a pseudogap at T*:

    a. Disorder-rounded first order transition to a broken symmetry phase (hidden?)
    b. Precursors of long-range order in d=2
    c. Mott Physics

2. What does theory have to say about these different possibilities, in particular, what are the experimental signatures in transport and every other probe that distinguish these different possibilities?

3. What is the role of disorder overall?

4. Amongst e-doped cuprates, iron based SC, heavy fermions and organics, (or other) what are the materials where we agree that one or the other mechanism has been “proven” beyond reasonable doubt? (No discussion of h-doped at this point).

5. What are the zero-temperature phases in the cuprates that have been unambiguously identified? dFF-DW, PDW, AFM, dSC, loop currents, other …

    a. What makes these phases special compared to what has been observed in other materials.
    b. How do these phases reconstruct the Fermi surface? Or do they?

6. What are the materials where an AFM or a CDW quantum critical point with surrounding d-SC dome has been established to everyone’s satisfaction?

    a. (What is the smoking gun to say that superconductivity is a simple consequence of the QCP?)

7. What causes the bad metal phase in h-doped cuprates? (Is there such a phase in the e-doped cuprates? In other SC materials?)

8. What causes the pseudogap in h-doped cuprates?

9. It seems that the mechanism for superconductivity in iron pnictides is much less controversial than in high Tc.

    a. Is that correct and why?
    b. Did “realistic calculations” play an important role in this regard?

10. Do we agree on the mechanism for superconductivity in quasi one-dimensional superconductors (Bechgaard salts), quasi two-dimensional superconductors (BEDT, DMIT families), fullerenes, ruthenates, whatever…?

11. What is the mechanism for high-temperature superconductivity? The following questions perhaps help orient the discussion.

   a. Is there glue? What do we mean by that?
   b. What makes Tc go down on the left-hand side of the dome? (or what can we definitely rule out?)
   c. What makes Tc go up on the right-hand side of the dome? (or what can we definitely rule out?)

12. Wrap up.

    a. What do we agree on?
    b. What do we agree to disagree on?
    c. If we do not agree that the high Tc problem has been solved, (we hope we do) what will it take to reach that conclusion?

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