Optical and plasmonic properties of twisted bilayer graphene: Impact of interlayer tunneling asymmetry and ground-state charge inhomogeneity

Abstract

We present a theoretical study of the local optical conductivity, plasmon spectra, and thermoelectric properties of twisted bilayer graphene (TBG) at different filling factors and twist angles $\theta$. Our calculations are based on the electronic band structures obtained from a continuum model that has two tunable parameters, $u_0$ and $u_1$, which parametrize the intra-sublattice inter-layer and inter-sublattice inter-layer tunneling rate, respectively. In this Article we focus on two key aspects: i) we study the dependence of our results on the value of $u_0$, exploring the whole range $0\le u_0\le u_1$; ii) we take into account effects arising from the intrinsic charge density inhomogeneity present in TBG, by calculating the band structures within the self-consistent Hartree approximation. At zero filling factor, i.e. at the charge neutrality point, the optical conductivity is quite sensitive to the value of $u_0$ and twist angle, whereas the charge inhomogeneity brings about only modest corrections. On the other hand, away from zero filling, static screening dominates and the optical conductivity is appreciably affected by the charge inhomogeneity, the largest effects being seen on the intra-band contribution to it. These findings are also reflected by the plasmonic spectra. We compare our results with existing ones in the literature, where effects i) and ii) above have not been studied systematically. As natural byproducts of our calculations, we obtain the Drude weight and Seebeck coefficient. The former displays an enhanced particle-hole asymmetry stemming from the inhomogeneous ground-state charge distribution. The latter is shown to display a broad sign-changing feature even at low temperatures ($\approx 5\mathrm{K}$) due to the reduced slope of the bands, as compared to those of single-layer graphene.

28 pages, 16 figures, 6 appendices

References in corpus (8)

• Sub-diffractional, volume-confined polaritons in a natural hyperbolic material: hexagonal boron nitride
• Continuum Model of the Twisted Bilayer
• Fast and Sensitive Terahertz Detection Using an Antenna-Integrated Graphene pn Junction
• The crucial role of atomic corrugation on the flat bands and energy gaps of twisted bilayer graphene at the "magic angle" $\theta \sim 1.08^{\circ }$
• Optical Conductivity of Twisted Bilayer Graphene
• Quasi-flat plasmonic bands in twisted bilayer graphene
• High-order nonlinear optical response of a twisted bilayer graphene
• Generation and morphing of plasmons in graphene superlattices

Cited by in corpus (27)

• Quantum Nanophotonics in Two-Dimensional Materials
• Hydrodynamic approach to two-dimensional electron systems
• Nano-imaging photoresponse in a moiré unit cell
• Hydrodynamic collective modes in graphene
• Collective excitations and plasmon spectrum in twisted bilayer graphene near the magic angle
• Chirality-induced spin texture switching in twisted bilayer graphene
• Why the first magic-angle is different from others in twisted graphene bilayers: interlayer currents, kinetic and confinement energy and wavefunction localization
• Correlation-Driven Electron-Hole Asymmetry in Graphene Field Effect Devices
• Tunable interband and intraband plasmons in twisted double bilayer graphene
• Emerging chiral optics from chiral interfaces
• Effects of heterostrain and lattice relaxation on optical conductivity of twisted bilayer graphene
• Theory of intrinsic acoustic plasmons in twisted bilayer graphene
• Weak Coupling Theory of Magic-Angle Twisted Bilayer Graphene
• Berry curvature, spin Hall effect and nonlinear optical response in moiré transition metal dichalcogenide heterobilayers
• Flat and Correlated Plasmon Bands in Graphene/$\alpha$-RuCl${}_3$ Heterostructures
• Plasmonic Quantum Dots in Twisted Bilayer Graphene
• Moiré-Induced Transport in CVD-Based Small-Angle Twisted Bilayer Graphene
• Neutral magic-angle bilayer graphene: Condon instability and chiral resonances
• Layer Hall counterflow as a model probe of magic-angle twisted bilayer graphene
• Theoretical determination of the effect of a screening gate on plasmon-induced superconductivity in twisted bilayer graphene
• Magnetoplasmons in magic-angle twisted bilayer graphene
• Optical properties, plasmons, and orbital Skyrme textures in twisted TMDs
• Large quantum nonreciprocity in plasmons dragged by drifting electrons
• Layer-Resolved Quantum Transport in Twisted Bilayer Graphene: Counterflow and Machine Learning Predictions
• Ultrafast dynamics of quantum matter driven by time-energy entangled photons
• Sliding-dependent electronic structures of alternating-twist tetralayer graphene
• Plasmons in N-layer systems