Micro-ARPES study on the cuprate superconductor YBCO

Utilizing angle-resolve photoemission spectroscopy with several tens of microns spot size (micro-ARPES), we disentangled surface electronic inhomogeneity of the high-T_c cuprate superconductor YBa₂Cu₃O_7-δ. Two surface terminations consisting of either a CuO or BaO layer are identified through a chemical-states-specified core-level intensity distribution. This enables us to perform termination-selective ARPES measurements that uncover the different charge fillings and electronic configurations depending on the surface termination. By combining the real-space and electronic information, we propose a simple model to explain the termination-dependent surface electronic reconstruction. Further, we will also present new observations of peculiar superconducting states as well as zero-energy surface states on the heavily overdoped BaO surface.