The low-energy electron band structure of a two-dimensional Dirac nodal-line semimetal grown on a silicon surface

摘要

The low-energy electron band structure of Cu2Si on Si(111) has been investigated using angle-resolved photoemission spectroscopy. Cu2Si exhibits two Dirac nodal-lines, stemming from the crossing of one electron-pocket with two hole-pockets, that are protected by mirror reflection symmetry. When Cu2Si is placed on Si(111), the hole-pockets and their satellite bands due to the quasi-5x5 periodicity are clearly observed whereas the electron-pocket is observed with very weak spectral intensity. Interestingly, close to the Fermi energy, the hole-pockets exhibit almost linear energy-momentum dispersion when their spectral width is also linearly proportional to energy. These findings indicate that Cu2Si on Si(111) can host Dirac nodal-line fermions, of which low-energy excitations might depart from those of the conventional Fermi liquid.