Thermal and Quantum Fluctuations Induced Additional Gap in Single-particle Spectrum of d-p model

TL;DR

This paper investigates how thermal and quantum fluctuations induce an additional pairing gap in the single-particle spectrum of the d-p model, relevant for high-Tc superconductors, revealing complex anisotropic effects and the influence of spin degeneracy.

Contribution

It analytically demonstrates the emergence of an anomalous pairing gap due to fluctuations in the d-p model, highlighting the effects of spin degeneracy and potential access to quantum criticality.

Findings

Anomalous pairing gap _tq exists beyond the d-wave gap.

The pairing gap anisotropy is influenced by hopping and hybridization.

Quantum criticality may be masked at physical spin degeneracy N=2.

Abstract

The possibility of thermal and quantum fluctuations induced attractive interaction leading to a pairing gap \Delta_tq 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 sources, namely, nearest neighbour hoppings and the p-d hybridization but not the coupling of the effective interaction. The temperature at which \Delta_tq vanishes may be driven to zero by using a tuning parameter to have access to quantum criticality 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 space below the pairing gap \Delta_tq. Thus it appears that the reduction in spin degeneracy has the effect of masking quantum criticality.