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Research
Pseudogap
Early studies (1996) demonstrated that electronic excitations are gapped
even in the normal state of the high-Tc superconductors. This normal
state gap—termed a "pseudogap" because it is not
sharply defined, but rather has a broad spectral tail associated
with it—closes as one reaches optimal doping. The gap is highly
anisotropic and steals spectral weight preferrentially from the Brillouin
zone edges in the Fermi surface mapping below. Some have considered
this gap to signify pre-formed cooper pairs, and others have considered
it to be evidence of a competing state. This pseudogap, however,
has defied a resolution predominantly due to its peculiar line-shape
and its evolution with doping.
