Observation of a Folded Dirac Cone in Heavily Doped Graphene

Abstract

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.g., the Kekule-like distortion phase), accompanied by a bandgap opening. According to the findings, the replica Dirac band in Gd-intercalated graphene disappears beyond a critical temperature of 30 K and can be suppressed by potassium adsorption. The modulation of the replica Dirac band is primarily attributable to the residual frozen gas, which can act as a source of intervalley scattering at temperatures below 30 K. Our results highlight the persistence of the hidden Kekule-like phase within the heavily doped graphene, enriching our current understanding of its replica Dirac Fermions.

Bipolar electron waveguides in two-dimensional materials with tilted Dirac cones

“…In graphene, the tilting of Dirac cones can be induced through various means, e.g. via the application of mechanical strain [31,[44][45][46][47], doping [48], or the application of external electric [49][50][51][52][53][54][55] or magnetic potentials [56,57]. An alternative approach to studying systems that support tilted Dirac cones involves exploring the connection between gravitational physics and condensed-matter systems [58][59][60][61][62][63][64].…”