Photoemission orbital tomography based on tight-binding approach: method and application to π-conjugated molecules

Conventional photoemission orbital tomography based on Fourier iterative method enables us to extract a projected two-dimensional (2D) molecular orbital from a 2D photoelectron momentum map (PMM) of planar π-conjugated molecules in a single-orientation system, while not in a multi-orientation system. In this work, we demonstrate photoemission orbital tomography for π-conjugated molecules with a tight-binding ansatz (linear combination of atomic orbitals). We analyze 2D PMMs of single-orientation pentacene/Ag(110) and multi-orientation 3,4,9,10-perylenetetracarboxylic dianhydride/Ag(110) and reproduce their three-dimensional highest occupied molecular orbitals. We demonstrate that the PhaseLift algorithm can be used to analyze PMM including experimental or theoretical uncertainties. With the 2D PMM for pentacene, we simultaneously optimized the structure and the molecular orbital. The present approach enables us to extract the three-dimensional orbitals and structures of existing materials.