From BRYAN COLES
‘Electrons switch on to heavy metal’, 19 May, was a valiant and overall
a successful attempt to give a flavour of the heavy fermion materials.
However, as well as correcting the name of Zachary Fisk, I must point
out that the discovery of heavy fermion materials did not emerge from a
search for new superconductors but from basic research in magnetism of alloys.
Also, the Fermi surface enclosing occupied states is in wave-vector
space. Finally, the unusual character of superconductivity in these materials
is most strongly indicated by the growing evidence that magnetic fluctuations,
not lattice vibrations, provide the mechanism that couples the quasi-particles
into pairs.
Bryan Coles Imperial College, London
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