Engineering Metal-sp_xy Dirac Bands on the Oxidized SiC Surface

Abstract

The ability to construct 2D systems, beyond materials natural formation, enriches the search and control capability of new phenomena. For instance, the synthesis of topological lattices of vacancies on metal surfaces through scanning tunneling microscopy. In the present study we demonstrate that metal atoms encaged in silicate adlayer on silicon carbide is an interesting platform for lattices design, providing a ground to experimentally construct tight-binding models on an insulating substrate. Based on the density functional theory, we have characterized the energetic and the electronic properties of 2D metal lattices embedded in the silica adlayer. We show that the characteristic band structures of those lattices are ruled by surface states induced by the metal-s orbitals coupled by the host-pxy states; giving rise to spxy Dirac bands neatly lying within the energy gap of the semiconductor substrate.In recent years two-dimensional (2D) materials have emerged with prominent phenomena and applications. For instance, graphene, the first observed 2D material, presents relativistic quasiparticles described by the massless Dirac equation [1]; meanwhile many other materials have been theoretically predicted [2, 3] and experimentally synthesized [4]. Within these, new quasiparticles [5][6][7][8], and topological/semimetal phases [9][10][11] have attracted great interest in fundamental physics. Focusing in technological applications, quantum Hall effects (spin [12,13], anomalous [14,15] and valley [16]) and thermoelectric properties, to cite a few, are explored for devices engineering based on 2D systems [17][18][19][20][21].The ability to construct lattices on demand promotes the exploration/enhancement of the materials properties. Currently, we are facing a striking synergy between theoretical exploration and experimental lattices designs. For instance, artificial graphene has been constructed in quantum dots systems [22] and in 2D electron gas [23] allowing the control of the Dirac quasiparticles and topological phases [24]. Beyond these systems, within the organic chemistry, covalent organic frameworks and metal organic frameworks have been successfully synthesized by combining different molecules/metal centers [25][26][27].Further control over lattice formation has been exploited through scanning tunneling microscopy (STM) techniques "printing" atom-by-atom on solid surfaces, where the STM tip brings precise control over the lattice formation [28][29][30][31]. For instance, topological states have been engineered on atomic square lattice in chlorine covered Cu(100) surface by vacancy formation [32]. Changing the substrate surface to Cu(111) lieb lattice [33], graphene-like [34] and quasicristals [35] have been imprinted in a carbon monoxide cover layer, while fractal geometric lattices have been achieved in Co covered Cu(111) [36]. Those studies took advantage of the current state of the art on the control over the atomic and molecular adsorption/desorption processes on metal surfaces. However, it is worth pointing...

Bandgap evolution in nanographene assemblies

“…By assembling it in different structures, we found a gap reduction. The control of molecules' position on surfaces and nano-patterning in graphene allows the precise gen-eration of structures [42][43][44][45] . Here we explore different cycloarene assemblies by varying the number of bonds between neighboring molecules and the lattice geometry.…”

Structural Transition in Oxidized Ca2N Electrenes: CaO/CaN 2D Heterostructures

“…For instance, the encapsulation of the Ca 2 N nanosheet using 2D shields such as graphene, single layer of BN, or graphane . On the other hand, NFE states make the Ca 2 N surface quite an interesting platform to perform atomic design on 2D materials, for instance, through functionalization by foreign atoms or molecules. − Indeed, OH-functionalized Ca 2 N and Y 2 C MLs have been proposed as new 2D materials for application in ion batteries; and very recently, the control of the electronic and magnetic properties in Ca 2 N MLs through hydrogenation and oxidation processes has been proposed. , …”

High-degeneracy points protected by site-permutation symmetries

“…Therefore, the Γ point degeneracies in the kagome lattice and the pseudospin-2 Dirac quasiparticle of the snubhexagonal lattice are robust against long range isotropic interactions. Particularly, for the snub-hexagonal, the space group predicts a twofold degeneracy, while the sitepermutation symmetry shows that a fivefold symmetry is always preserved at Γ [47].…”

“…The snub-hexagonal lattice can be grown with MOF surface self-assembly [42,43], and in a stable boron 2D allotrope [44,45]. Still within borophene polymorphs, a structure similar to the triangular-rectangular lattices have been experimentally found [46], while a square-octagon lattice has been shown in a carbon 2D allotrope [47].…”