Realization of a Two-Dimensional Checkerboard Lattice in Monolayer Cu₂N

Two-dimensionalcheckerboard lattice, the simplest line-graphlattice,has been intensively studied as a toy model, while material designand synthesis remain elusive. Here, we report theoretical predictionand experimental realization of the checkerboard lattice in monolayerCu(2)N. Experimentally, monolayer Cu2N can berealized in the well-known N/Cu(100) and N/Cu(111) systems that werepreviously mistakenly believed to be insulators. Combined angle-resolvedphotoemission spectroscopy measurements, first-principles calculations,and tight-binding analysis show that both systems host checkerboard-derivedhole pockets near the Fermi level. In addition, monolayer Cu2N has outstanding stability in air and organic solvents, which iscrucial for further device applications.