The origin of the pseudogap is controversial and still subject to debate in the condensed matter community. Two main interpretations are emerging:
1. The scenario of preformed pairs In this scenario, electrons form pairs at a temperature
T* that can be much larger than the critical temperature
Tc where superconductivity appears. Values of
T* of the order of 300 K have been measured in underdoped cuprates where
Tc is about 80 K. The superconductivity does not appear at
T* because large phase fluctuations of the pairing field cannot order at this temperature. The pseudogap is then produced by incoherent fluctuations of the pairing field. The pseudogap is a normal state precursor of the superconducting gap due to local, dynamic pairing correlations. This point of view is supported by a quantitative approach of the attractive pairing model to specific heat experiments.
2. The scenario of a non-superconductivity-related pseudogap In this class of scenarios, many different possible origins have been put forward, such as the formation of
electronic stripes,
antiferromagnetic ordering, or other exotic
order parameters competing with superconductivity. ==References==