A pseudogap is a partial suppression of low-energy spectral weight without all the properties of a fully developed energy gap. In high-temperature superconductors it is identified through several probes and can occur outside the superconducting phase.
A depletion in a spectrum does not by itself establish a particular order parameter or pairing mechanism. Different measurements weight different momenta and excitations, so temperature and momentum dependence help distinguish competing explanations. The term names an observed class of behavior while leaving its microscopic interpretation to further evidence.[ref]
The pseudogap: friend or foe of high Tc? by Michael R. Norman and others. review of phenomenology and interpretations
The pseudogap refers to a phenomenon observed in certain condensed matter systems, particularly in high-temperature superconductors, where a partial gap in the excitation spectrum appears in a material's electronic density of states at temperatures above the superconducting transition temperature (Tc). This gap is considered "pseudo" because it does not exhibit the full characteristics of an energy gap present in conventional superconductivity.
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