Electronic theory for scanning tunneling microscopy spectra in bilayer nickelate thin films

Abstract

Recent Scanning Tunneling Microscopy (STM) experiments measuring the superconducting gap features in thin films of superconducting bilayer nickelates La2PrNi2O7 at ambient pressure and compressive strain paved the way to study the Cooper-pairing models and the band-selective identification of the gap features in these systems. Here, using the realistic two-orbital bilayer model and the continuum Green's function formalism, we theoretically analyze orbital and band-selective local density of states as well as the corresponding STM spectra. We find that the multiorbital character and the spatial dependence of the Wannier functions leads to the spectra developing characteristic features depending on the position of the scanning tunneling microscope's tip. This allows for a band-resolved analysis of the superconducting coherence peaks and scattering momenta. We identify a clear path for experimental measurements to not only identify the debated incipiency of the gamma-band, but also identification of the coherence peaks' band origins via distance dependent measurements of the local density of states and its corrections through impurity scattering.