Plasmons in graphene moiré superlattices

Abstract

Moiré patterns are periodic superlattice structures that appear when two crystals with a minor lattice mismatch are superimposed. A prominent recent example is that of monolayer graphene placed on a crystal of hexagonal boron nitride. As a result of the moiré pattern superlattice created by this stacking, the electronic band structure of graphene is radically altered, acquiring satellite sub-Dirac cones at the superlattice zone boundaries. To probe the dynamical response of the moiré graphene, we use infrared (IR) nano-imaging to explore propagation of surface plasmons, collective oscillations of electrons coupled to IR light. We show that interband transitions associated with the superlattice mini-bands in concert with free electrons in the Dirac bands produce two additive contributions to composite IR plasmons in graphene moiré superstructures. This novel form of collective modes is likely to be generic to other forms of moiré-forming superlattices, including van der Waals heterostructures.

Graphene-plasmon polaritons: From fundamental properties to potential applications

“…Both papers provide real-space imaging of GPPs with extremely high spatial resolution (∼20 nm) limited only by the dimensions of the AFM probe. s-SNOM has been intensively used, e.g., for exploration of plasmons in graphene Moiré superlattices [63], for observation of ultraslow hyperbolic polariton propagation [64], and for observation of hyperbolic phonon-polaritons in boron nitride [65]. More recently, Alonso-González et al [66] utilized an immovable metal gold rod standing on a graphene sheet as another kind of antenna.…”

Harmonic model of corrugations of incommensurate two-dimensional layers

“…The plot in Fig. 4(a) We now apply our model to the realistic 57C/56BN-R0° system, which has the experimentally observed [12,18,22] moiré-cell size of 14 nm. Fig.…”

“…We expect the properties of such high-quality graphene heterostructures to be particularly sensitive to the sub-nanometer corrugations arising from the interaction between graphene and substrate lattices. Indeed, the moiré superlattices of graphene on BN have been implicated in the opening of an electronic gap at the Dirac point [13,14,15,16,17] and the emergence of electronic minibands [2,14,18], and are believed to affect optical [2,18] and magnetic properties [2].…”

Real-Space Imaging of the Tailored Plasmons in Twisted Bilayer Graphene

“…Indeed, the 2D nature of graphene makes it extremely sensitive to interlayer coupling that could dramatically modify the properties of Dirac fermions and their plasmonic excitations. For example, earlier studies about Bernal-stacked bilayer graphene (BLG) [20,22] and graphene/hBN heterostructures [23,24] have demonstrated many unique plasmonic characteristics compared to those of SLG.…”

“…1(a), the infrared light (solid arrow) from a continuous-wave infrared laser is focused at the apex of a metalized AFM tip. The laser-illuminated tip acts as both a launcher and a detector of surface plasmons [13][14][15][16][17][18][19][20][21][22][23]. The backscattered light (dashed arrow) off the tip-sample system contains essential information about plasmons underneath the tip.…”