Optoelectronic Fingerprints of Interference between Different Charge Carriers in Graphene Superlattices and Analogies to Twisted Graphene Bilayers

TL;DR

This paper investigates the optoelectronic properties of graphene superlattices with Kekulé patterns, revealing interference effects between different charge carriers and drawing analogies to twisted bilayer graphene, with implications for understanding quasiparticle behavior.

Contribution

It introduces a theoretical analysis of optoelectronic signatures in Kekulé-patterned graphene superlattices, highlighting carrier interference and similarities to multifold fermions and twisted bilayer graphene.

Findings

Multiple carrier species with distinct effective masses identified.

Characteristic peaks in optical conductivity suggest interference effects.

Band merging and flattening resemble twisted bilayer graphene phenomena.

Abstract

Motivated by recent experimental findings on the low-energy spectrum of Kekul\'e-patterned graphene, the optoelectronic signatures of graphene superlattices with a spatial modulation that triples the size of the unit cell and folds the valleys to the center of the Brillouin zone are studied. For superlattices like those visualized in recent experiments, the optoelectronic response reveals multiple species of carriers distinguished by their effective masses or Fermi velocities. Their signatures are similar to those of systems hosting multifold fermions in which different frequency intervals are dominated by different types of quasiparticles. Remarkably, the response of these systems exhibits a characteristic peak in the optical conductivity suggesting a kind of interference between the different species of carriers. We also discuss a related superlattice that exhibits merging Dirac cones and band flattening, with a Hamiltonian that resembles a version of the chiral model for twisted bilayer graphene where the long-range moir\'e modulation has been substituted by a two-parameter bias.