Fig. 1: Concept of CuO2 intra-unit-cell orbital order.
a, Signatures of nematic phase appearing at the cuprate pseudogap (PG) temperature T*(p). Each data point is the average of multiple measurements from each technique (Methods). AF represents the antiferromagnetic state and DSC represents d-wave superconductivity. The error bars are accordingly derived from these estimates. b, Schematic of the relevant orbitals in the CuO2 plane depicting the crucial inter-oxygen-orbital Coulomb interaction Vpp. c, Degeneracy of the Cu \(3d_{x^2-y^2}\) orbital (grey) is lifted by the Coulomb energy U. The px orbital of the oxygen along the x axis of the Cu atom (red) is separated from the upper Cu band by the charge transfer energy εx. At the oxygen site along the y axis from the Cu atom (blue), the py orbital is separated from the upper Cu band by the charge transfer energy εy. d, Schematic of the density of electronic states (top) where the Coulomb energy U and charge transfer energy ε are indicated. Typical measured differential conductance g(V) spectrum (bottom) where the top of the lower band and the bottom of the upper band are visualized, their separation being a direct measure of charge transfer energy ε (ref. 25). CTB represents the charge transfer band, LHB represents the lower Hubbard band and UHB represents the upper Hubbard band.
