Surface termination and electronic reconstruction in YBa2Cu3O7−δ

We present a spatially resolved angle-resolved photoemission spectroscopy (ARPES) study on the Y-based high-${T}_{c}$ cuprate superconductor ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ to disentangle surface electronic inhomogeneity. 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. Our results demonstrate a significant importance of the spatially resolved ARPES in order to obtain intriguing electronic information, particularly from surface-inhomogeneous systems.