Observation of a Folded Dirac Cone in Heavily Doped Graphene.

Superlattice potentials imposed on graphene can alter its Dirac states, enabling the realization of various quantum phases. We report the experimental observation of a replica Dirac cone at the Brillouin zone center induced by a superlattice in heavily doped graphene with Gd intercalation using angle-resolved photoemission spectroscopy (ARPES). The replica Dirac cone arises from the (√3× √3)R30° superlattice formed by the intervalley coupling of two nonequivalent valleys (e.

Thickness-Dependent Evolutions of Surface Reconstruction and Band Structures in Epitaxial Thin Films.

Ferroelectric materials have received great attention in the field of data storage, benefiting from their exotic transport properties. Among these materials, the two-dimensional (2D) InSe has been of particular interest because of its ability to exhibit both in-plane and out-of-plane ferroelectricity. In this article, we realized the molecular beam epitaxial (MBE) growth of films on bilayer graphene (BLG) substrates with precisely controlled thickness.

Inducing itinerant ferromagnetism by manipulating van Hove singularity in epitaxial monolayer 1T-VSe.

The itinerant ferromagnetism can be induced by a van Hove singularity (VHS) with a divergent density of states at Fermi level. Utilizing the giant magnified dielectric constant ε of SrTiO(111) substrate with cooling, here we successfully manipulated the VHS in the epitaxial monolayer (ML) 1T-VSe film approaching to Fermi level via the large interfacial charge transfer, and thus induced a two-dimensional (2D) itinerant ferromagnetic state below 3.3 K.

Suppression of Intervalley Coupling in Graphene via Potassium Doping.

The quantum interference patterns induced by impurities in graphene can form the (√3 × √3)R30° superlattice with intervalley scattering. This superlattice can lead to the folded Dirac cone at the center of Brillouin zone by coupling two non-equivalent valleys. Using angle-resolved photoemission spectroscopy (ARPES), we report the observation of suppression of the folded Dirac cone in mono- and bilayer graphene upon potassium doping.

Epitaxial Growth of Uniform Single-Layer and Bilayer Graphene with Assistance of Nitrogen Plasma.

Graphene was reported as the first-discovered two-dimensional material, and the thermal decomposition of SiC is a feasible route to prepare graphene films. However, it is difficult to obtain a uniform single-layer graphene avoiding the coexistence of multilayer graphene islands or bare substrate holes, which give rise to the degradation of device performance and becomes an obstacle for the further applications. Here, with the assistance of nitrogen plasma, we successfully obtained high-quality single-layer and bilayer graphene with large-scale and uniform surface via annealing 4H-SiC(0001) wafers.

Direct Observation of Global Elastic Intervalley Scattering Induced by Impurities on Graphene.

The scattering process induced by impurities in graphene plays a key role in transport properties. Especially, the disorder impurities can drive the ordered state with a hexagonal superlattice on graphene by electron-mediated interaction at a transition temperature. Using angle-resolved photoemission spectroscopy (ARPES), we reveal that the epitaxial monolayer and bilayer graphene with various impurities display global elastic intervalley scattering and quantum interference below the critical temperature (34 K), which leads to a set of new folded Dirac cones at the Brillouin-zone center by mixing two inequivalent Dirac cones.