Thermal signatures of pairing correlations in nuclei and nano-scale   metallic grains
  Atomic nuclei and nano-scale metallic grains are in the crossover regime of pairing correlations between the bulk limit, where the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity is valid, and the fluctuation-dominated regime, where BCS theory breaks down. In this fluctuation-dominated regime, the pairing gap is comparable to or smaller than the single-particle mean level spacing. We discuss thermal signatures of pairing correlations in nuclei and ultra-small metallic grains that survive despite the large fluctuations of the pairing field. 
Y. Alhassid
nucl-th cond-mat.mes-hall cond-mat.str-el cond-mat.supr-con