Momentum-structure of remnant Mott-gap in prototype hole doped cuprates

Momentum dependent charge excitation of 2D cuprate class La2−xSrxCuO4 with different hole-doping levels (x) is measured using high resolution resonant inelastic X-ray scattering. Although a low-energy continuum is built up with doping, a remnant excitation gap behavior continues to exist even in highly doped metallic phase which we have studied in some detail. The excitation of the Mott gap becomes less dispersive with the increase of doping level and suggests a many-body coupling between charge fluctuation and magnetic character of the lattice. The results can be described within the framework of t–t′–t″–U model.