Electronic structure of the YCrB4 crystal surface, studied by micro-focused photoemission spectroscopy

We have performed a comprehensive electronic characterization of the needle-like single crystal YCrB₄ metal boride, prepared by cleavage, characterized using angle-resolved photoemission spectroscopy with a microfocused beam. Our findings reveal the three-dimensional (3D) band structure of YCrB₄, with band dispersions closely aligning with the first-principles calculations, confirming it is a topologically trivial insulator with a narrow band gap. Furthermore, a new metallic surface band was observed after cleavage, likely due to a space charge layer of the electron accumulation type. This study highlights the pivotal role of surface phenomena in shaping the electronic structure of YCrB₄ and provides insights into the interplay between bulk and surface states, offering a path for exploring its potential applications in surface-sensitive technologies.