Experimental observation of Dirac cones in artificial graphene lattices

On the problem of Dirac cones in fullerenes on gold

“…For specific binding energies one can obtain a CES pattern in registry with the mini-BZ of C 60 which resemble (though not exactly reproduce) contours of Dirac cones seen earlier for C 60 / Cu(111). 9 We emphasize that the illumination of peculiar arc/ parts of the replica and hence the overall occurrence of conical contours critically depends on the experimental geometry (the angle of light incidence, polarization of photons, and orientation of analyzer). One can therefore expect strong variations in the matrix elements of these features between different experimental setups.…”

“…The absence of Dirac cones and artificial graphene in the C 60 /Au(111) system is also confirmed by our DFT calculations. We prefer performing a simulation of the entire C 60 molecule on Au(111) instead of muffin-tin like exclusion potentials at molecular sites 9 (which, strictly speaking, do not reproduce a honeycomb lattice with its specific hopping integrals). The Au substrate was approximated as 3 atomic layers of Au.…”

“…Our results suggest that the realization of artificial graphene by a fullerene network may not be the only explanation for the Dirac cones reported earlier. 9 In the following we will demonstrate that the linear bands are merely mimicking Dirac cones, and instead derive from umklapp scattering of photoelectrons on the hexag-onal and perfectly periodic superlattice of fullereneswith no need for involvement of muffin-tin-like hollow potentials and without the realization of artificial graphene. Ultimately, we can attribute the formation of false Dirac cones exclusively to the diffraction in the final state of photoemission from the 2D surface-or subsurface-localized bands of Au(111) residing at the boundaries of the surface-projected bulk sp-band.…”

Engineering novel surface electronic states via complex supramolecular tessellations

“…Lately, it has been shown that using molecular self-assemblies, peculiar electronic lattices can also be obtained. 31,32 At the current stage, the potential of QD coupling schemes was not fully exploited as most previous studies concentrated on simple hexagonal porous networks, 33 which offer relatively simple band structures (BS), while modulating SS electrons in complex tessellations was rarely addressed. 34,35 Here, we report the tailoring of Ag(111) SS electrons via organometallic-tectonbased networks featuring the (3.6.3.6) and the (3.4.6.4) Archimedean tilings (AT).…”

“…Lately, it has been shown that using molecular self-assemblies, peculiar electronic lattices can also be obtained. 31,32…”