Pre-pairing and the "Filling" Gap in the Cuprates From the Tomographic   Density of States
  We use the tomographic density of states (TDoS), which is a measure of the density of states for a single slice through the band structure of a solid, to study the temperature evolution of the superconducting gap in the cuprates. The TDoS provides unprecedented accuracy in determining both the superconducting pair-forming strength, $\Delta$, and the pair-breaking rate, $\Gamma$. In both optimally- and under-doped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, we find the near-nodal $\Delta$ smoothly evolves through the superconducting transition temperature - clear evidence for the existence of pre-formed pairs. Additionally, we find the long observed `filling' of the superconducting gap in the cuprates is due to the strongly temperature dependent $\Gamma$. 
T. J. Reber, N. C. Plumb, Y. Cao, Z. Sun, Q. Wang, K. P. McElroy, H.   Iwasawa, M. Arita, J. S. Wen, Z. J. Xu, G. Gu, Y. Yos...
cond-mat.supr-con cond-mat.str-el