Nanoscopic filters as the origin of d-wave energy gaps

Abstract

A ferroelastic nanoscopic chequerboard pattern of pseudogaps and superconductive gaps has been resolved by scanning tunnelling microscopy (STM) on Bi₂Sr₂CaCu₂O_{8+ δ} (BSCCO). Using this pattern, one can derive (not assume) a macroscopic anisotropic d-wave superconductive energy gap that agrees well with angle-resolved photoemission spectroscopy and Fourier transform scanning tunnelling microscopy data. The derivation is orbital only (no spins); it explains chemical trends in Raman scattering peak positions and strengths, and it predicts an unexpected reversal of anisotropic Raman gap signatures between BSCCO and La_{2− x} Sr _x CuO₄ (LSCO), in good agreement with experiment.