The Two Energy Scales of Tunneling Spectra of Cuprate Superconductors

Abstract

The atomically resolved energy gap Δ(r) measured by Scanning Tunneling Microscopy has become a major challenge connecting to the nature of electronic states in cuprates superconductors. More recently, a two-energy-gap structure has been observed by many different experiments. We show that it is possible that the charge inhomogeneity gives rise to a potential barrier between the microscopic regions or grains that are the origin of these gaps. A larger Δ(r) is due to the single-particle bound states and the same potential gives rise to a smaller superconducting gap Δ d (r). These results support the two-gap scenario and give a clear interpretation to the pseudogap phase.