Bill Buyers

Issue 1.  What is soft mode of superconducting dome (cuprates)? Neutrons
suggest that the resonance energy (spin response) is directly coupled to
the SC unstability for pair coherence.  But it is NOT the mechanism for
the Cooper pairs (much higher energy scale).  Is the AF boundary sharp,
is it contiguous in YBCO (as suggested by resistivity-Ando and thermal
conductivity and Zhang?) or separate as in LSCO.

1a  What is the meaning of the very narrow central mode that appears at
extreme underdoping on a much lower energy scale than the rest of the
(gapless) spin response?

2.  What is the nature of the intervening phase (neutrons suggest slow or
static dynamics but only short-range spin order) - a 'glass' does not
tell us much.  Polarized neutrons show that when close to SC boundary we
are far from AF boundary. Especially spin response has triplet symmetry
unlike AF insulator with xy confined spins. 

3. What is role of holes in creating spin canting, spirals etc. - needed
to explain polarized neutons data.  Do we need pairs of holes to account
for canting -spirals. Is the theory and structure factor for pair-induced
rotation well established?