Two-energy-gap preformed-pair scenario for cuprate superconductors: Implications for angle-resolved photoemission spectroscopy

We show how, within a preformed-pair scenario for the cuprate pseudogap, the nodal and antinodal responses in angle-resolved photoemission spectroscopy necessarily have very different temperature T dependences. We examine the behavior and the contrasting T dependences for a range of temperatures both below and above T(c). Previously, the distinct nodal and antinodal responses have provided strong support for the two-gap scenario of the cuprates in which the pseudogap competes with superconductivity. Instead, our theory supports a picture in which the pseudogap derives from pairing correlations, identifying the two-gap components with noncondensed and condensed pairs. Our calculations are based on a microscopic diagrammatic approach for addressing pairing correlations in a regime where the attraction is stronger than BCS and the coherence length is anomalously short. This many body theory-based scheme takes as a starting point the BCS ansatz for the ground-state wave function and incorporates finite temperature effects through coupled equations for the single particle and pair propagators (or T matrix). It leads to reasonably good agreement with a range of different photoemission measurements in the moderately underdoped regime and we emphasize that here there is no explicit curve fitting. We briefly address the more heavily underdoped regime in which the behavior is more complex.