Theory of intrinsic acoustic plasmons in twisted bilayer graphene

Abstract

We present a theoretical study of the intrinsic plasmonic properties of twisted bilayer graphene (TBG) as a function of the twist angle $\theta$ (and other microscopic parameters such as temperature and filling factor). Our calculations, which rely on the random phase approximation, take into account four crucially important effects, which are treated on equal footing: i) the layer-pseudospin degree of freedom, ii) spatial non-locality of the density-density response function, iii) crystalline local field effects, and iv) Hartree self-consistency. We show that the plasmonic spectrum of TBG displays a smooth transition from a strongly-coupled regime (at twist angles $\theta \lesssim 2^{\circ }$), where the low-energy spectrum is dominated by a weakly dispersive intra-band plasmon, to a weakly-coupled regime (for twist angles $\theta \gtrsim 2^{\circ }$) where an acoustic plasmon clearly emerges. This crossover offers the possibility of realizing tunable mid-infrared sub-wavelength cavities, whose vacuum fluctuations may be used to manipulate the ground state of strongly correlated electron systems.

11 pages, 4 figures + Supplemental Material

References in corpus (22)

• Flat Bands in Slightly Twisted Bilayer Graphene
• Continuum Model of the Twisted Bilayer
• Moiré heterostructures as a condensed matter quantum simulator
• Lattice relaxation and energy band modulation in twisted bilayer graphenes
• Strong Coulomb drag and broken symmetry in double-layer graphene
• Cavity Quantum Materials
• The crucial role of atomic corrugation on the flat bands and energy gaps of twisted bilayer graphene at the "magic angle" $\theta \sim 1.08^{\circ }$
• Ultra-high quality two-dimensional electron systems
• Eliashberg Theory: a short review
• Quantum Nanophotonics in Two-Dimensional Materials
• Minimum Conductivity and Evidence for Phase Transitions in Ultra-clean Bilayer Graphene
• Chiral response of twisted bilayer graphene
• Collective excitations in twisted bilayer graphene close to the magic angle
• Quasi-flat plasmonic bands in twisted bilayer graphene
• Chiral plasmons with twisted atomic bilayers
• Optical and plasmonic properties of twisted bilayer graphene: Impact of interlayer tunneling asymmetry and ground-state charge inhomogeneity
• Superconductivity from collective excitations in magic angle twisted bilayer graphene
• Generation and morphing of plasmons in graphene superlattices
• Plasmon-enhanced near-field chirality in twisted van der Waals heterostructures
• Theory of the Pseudospin Resonance in Semiconductor Bilayers
• Working principles of doping-well structures for high-mobility two-dimensional electron systems
• Valley splitter and transverse valley focusing in twisted bilayer graphene

Cited by in corpus (5)

• Roadmap for Photonics with 2D Materials
• Roadmap on Nonlocality in Photonic Materials and Metamaterials
• Many-body perturbation theory for moiré systems
• Two-dimensional moiré phonon polaritons
• Plasmons in N-layer systems