Normal-state pseudogap

In summary the account of interband vibronic interactions in the doping-dependent electron spectmm of cuprates allows to explain the presence of two normal state pseudogaps at underdoping and the extent of the pseudogap behaviour to the whole doping region. Such results are far away from the basic Jahn-Teller effect framework and illustrate the brightness of the basic vibronic hybridization idea. 

It is seen that in the normal state A/ and Av survive and can be interpreted as the large and small pseudogap. Passing on to the optimal doping (c > Cp, c... 

Figure 1 3 1. Energetic characteristics of a model cuprate on the doping scale. 1 - the underdoped state small pseudogap As 2 - the large pseudogap A, 3 - the defect system superconducting gap Aa 4 - the itinerant system superconducting gap Ay 5 - Tc. The insert shows normal state gaps. p = 0.18 Pp- 0.12 0 0.23 p(Tcm) = 0.23]...

Abstract We will summarize here some of our measurements of the superconducting fluctuations effects on the in-plane electrical resistivity (the so-called in-plane para-conductivity) in La2-i-SrTCu04 thin films with different Sr content. Our results suggest that these superconducting fluctuations effects are not related to the opening of a pseudogap in the normal-state of underdoped compounds. 

Transport properties above Tc(x) Actually, it is not necessary to study the properties near T = 0 to rule out a pseudogap region beyond an xc in the superconducting range of x. If fig. (2) were true, the universal normal state anomalies would change to the pseudogap properties for any x for temperatures below T (x) and above Tc(x). The data does not sustain this point of view. 

A depression in this continuum at low frequency has widely been interpreted as evidence of the superconducting gap, but its presence in the normal state in underdoped samples originally cast doubt on this interpretation (Slakey et al. 1990). It is now becoming clear that this depression may well be associated with the pseudogap and that the Raman spectrum has parallels with the ab-plane scattering-rate spectrum (Blumbeig et al. 1997). 

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