Evidence on the pseudogap and condensate from the electronic specific heat

Evidence on the nature and hole density (p) dependence of the normal state pseudogap is obtained from the electronic Specific heat of several cuprate series, including new data for Bi:2212. The pseudogap energy decreases as E -g(p) similar to J(1 - p/p(crit)) for p < p(crit) and is zero for p > p(cri t). where p(crit) similar to 0.19 is close to optimal T-c. This is correlat ed with an abrupt crossover from weak to strong superconductivity at p(crit ). We conclude that the pseudogap is an intrinsic feature of the normal sta te density of states that competes with the condensate for low energy spect ral weight and is not related to precursor superconducting fluctuations. Th e linear p-dependencies of the entropy, the superfluid density and the stat es-non-conserving pseudogap are all interrelated. and appear to reflect str ong correlations in the doped Mott insulator. (C) 2000 Elsevier Science Ltd . All rights reserved.