Thermal and quantum fluctuations induced additional gap in single-particle spectrum of d-p model

The possibility of thermal and quantum fluctuations induced attractive interaction leading to a pairing gap Δtq in the single-particle spectrum of d-p model in the limit of a large N of fermion flavor is investigated analytically. This is an anomalous pairing gap in addition to the one with d-wave symmetry originating from partially screened, inter-site coulomb interaction. The motivation was to search for a hierarchy of multiple many-body interaction scales in high-Tc superconductor as suggested by recent experimental findings. The pairing gap anisotropy stems from more than one source, namely, nearest neighbor hoppings and the p-d hybridization, but not the coupling of the effective interaction. The temperature at which Δtq vanishes may be driven to zero by using a tuning parameter to have access to quantum criticality (QC) only when N⪢1. For the physical case N=2, the usual coherent quasi-particle feature surfaces in the spectral weight everywhere in the momentum below the pairing gap Δtq. Thus it appears that the reduction in spin degeneracy has the effect of masking quantum criticality.