Thursday, October 28, 2010

A Reconstructed view of the "Fermi surface".

Mike Norman writes some of the nicest and most helpful review articles about the cuprate superconductors. They are balanced and insightful. This week at the cake meeting we are discussing his latest, Fermi surface re-construction and the origin of high-temperature superconductivity. It gives a succinct summary of the issues raised by the observation of quantum oscillations associated with Fermi surface features iin the underdoped cuprates. It is impressive the way Norman is so objective and does not push any of his own significant contributions as being the "answer".

A few things I learnt

The importance of the negative sign of the Hall constant.

One can only produce electron pockets near x=1/8 with a magnetic stripe potential.

It is not clear where the "spin zeroes" associated with quantum oscillations are.

A few minor comments

Perhaps he gives too much credit to the initial claims from 1992 of observation of quantum oscillations, based on explosive experiments at Los Alamos. He mentioned criticisms by Springford et al. that the data was all noise. Should people get any credit for making unjustified claims based on dodgy data, just because the claimed effect turns out to be real. 

The unresolved issue of closed Fermi surface pockets vs. open arcs is perhaps not emphasized enough. Perhaps Norman leans too much towards pockets.

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