Fermi Velocity Reduction of Dirac Fermions around the Brillouin Zone Center in In₂Se₃–Bilayer Graphene Heterostructures

Abstract

Recently, graphene-based heterostructures and twisted bilayer graphene (TBG) have been studied intensively due to their novel physics and promising properties such as strong light-matter interaction, [1][2][3][4][5][6][7][8] quantum phase transition, [9] correlated insulator, [2] unconventional superconductivity, [1] fractional quantum

Thickness-Dependent Evolutions of Surface Reconstruction and Band Structures in Epitaxial β–In2Se3 Thin Films

“…Since the one-dimensional distortion on the threefolded rotational symmetric β-In 2 Se 3 lattice will have three equivalent orientations, this (9 × 1) reconstruction only appears as a set of weak peaks in the RHEED pattern shown in Figure 1k. We speculate the disappearance of the (9 × 1) distortion in ML β-In 2 Se 3 may be attributed to generalized Umklapp scattering induced by the graphene-based superlattice since the wave vector of the ML β-In 2 Se 3 is roughly ~√3 times the graphene one with an in-plane rotation of ~30 • [60,61]. This superlattice will induce the moiré Dirac cone and will be discussed later.…”

“…This weak Dirac cone was not observed in the 4 and 10 ML β-In 2 Se 3 films. The second derivative spectra in Figure 4f imply that this weak Dirac cone at Γ point has the characteristics of epitaxial graphene on SiC [60,69], which can be attributed to the Umklapp scattering in the β-In 2 Se 3 /BLG heterostructure [60]. This emergence of renormalized moiré Dirac cones suppresses the formation of (9 × 1) surface reconstruction and makes the ML β-In 2 Se 3 /BLG heterostructure a semi-metal, which contrasts with the semiconductive multilayer β-In 2 Se 3 films [Figure 4g,h].…”

Modified Dirac Fermions in the Crystalline Xenon and Graphene Moiré Heterostructure

“…[7][8][9][10] Instead, their 2D nature makes each crystal very sensitive to the potential induced by an adjacent layer, so that the misorientation between stacked 2D crystals imposes a new periodicity at the interface. [11][12][13] Resultant Moiré potential with a long periodicity folds the electron band structure of each crystal into a much smaller Brillouin zone, resulting in heavily modified electronic structures and a variety of novel electronic phases, including unconventional superconductivity, [14] Mott insulating phase, [15] ferromagnetism, [16] and ferroelectricity. [17] Periodic adsorption of foreign atoms on a 2D material plays a similar role as the stacked 2D crystals.…”

Observation of a Folded Dirac Cone in Heavily Doped Graphene

“…In our experiments, the replica Dirac cone disappears beyond 30 K but can reemerge upon subsequent cooling. In reality, the (√3 × √3)­R30° superlattice imposed on the Bloch wave induces the folding of the first BZ, leading to band folding and gap opening in graphene. ,− However, the underlying mechanism prompting the formation and transition of this temperature-dependent superlattice phase remains elusive. This phase transition observed on Gd-intercalated graphene appears to resemble a CDW-like process that freezes gas on graphite to form a (√3 × √3)­R30° superlattice .…”