Angle-resolved photoelectron spectroscopy of the ( 8.88 × 8.88 ) incommensurate surface reconstruction of Cu on Ge(111)

In this study we revisit the properties of the $("8.88\ifmmode\times\else\texttimes\fi{}8.88")\mathrm{R}{30}^{\ensuremath{\circ}}$ surface reconstruction obtained by evaporation of Cu on Ge(111), motivated by the predictions of Dirac nodal lines in two-dimensional ${\mathrm{Cu}}₂\mathrm{Ge}$ monolayer. After providing an updated version of the band structure of Ge(111) by angle-resolved photoemission (ARPES), we present the band structure of the $\mathrm{Cu}/\mathrm{Ge}(\mathrm{111})\text{\ensuremath{-}}(8.88\ifmmode\times\else\texttimes\fi{}8.88)\mathrm{R}{30}^{\ensuremath{\circ}}$ surface, which presents two surface bands, with having linear dispersion at the Fermi level.