θ-Tunable Photoluminescence from Interlayer Excitons in Twisted Bilayer Graphene

Abstract

Using resonant 2-photon excitation of interlayer electrons in twisted bilayer graphene (tBLG), we resolve photoluminescence (PL) that tunes spectrally with stacking angle, θ. This weak signal is 4- 5$\times$ larger than the non-resonant background and is emitted from the interlayer band anti-crossing regions traditionally associated with van Hove singularity resonances. However, our observation of resonant PL emission with delayed ~1 ps electronic thermalization suggests interlayer carriers may instead form bound-excitons. Using both the 2-photon PL and intraband transient absorption spectra, we observe bright and dark state peak-splitting associated with an interlayer exciton binding energy ranging from 0.5 to 0.7 eV for θ = 8${}^o$ to 17${}^o$. These results support theoretical models showing interlayer excitons in tBLG are stabilized by a vanishing exciton-coupling strength to the metallic continuum states. This unexpected dual metal-exciton optical property of tBLG suggests possible θ-tuneable control over carrier thermalization, extraction and emission in optical graphene-based devices.

References in corpus (25)

• Magic-angle graphene superlattices: a new platform for unconventional superconductivity
• Correlated Insulator Behaviour at Half-Filling in Magic Angle Graphene Superlattices
• Observation of Van Hove singularities in twisted graphene layers
• Probing Excitonic Dark States in Single-layer Tungsten Disulfide
• Excitonic Effects and Optical Spectra of Single-Walled Carbon Nanotubes
• Single Layer Behavior and Its Breakdown in Twisted Graphene Layers
• Raman spectroscopy study of rotated double-layer graphene: Misorientation-angle dependence of electronic structure
• Ultrafast Photoluminescence from Graphene
• Seeing many-body effects in single- and few-layer graphene: Observation of two-dimensional saddle-point excitons
• Probing dark excitons in atomically thin semiconductors via near-field coupling to surface plasmon polaritons
• Measurement of high exciton binding energy in the monolayer transition-metal dichalcogenides WS2 and WSe2
• Reduction of Fermi velocity in folded graphene observed by resonance Raman spectroscopy
• Nonlinear Photoluminescence in Atomically Thin Layered WSe2 Arising from Diffusion-Assisted Exciton-Exciton Annihilation
• The Interlayer Shear Modes in Twisted Multi-layer Graphenes: Interlayer coupling, Davydov Splitting and Intensity Resonance
• Van Hove Singularities and Excitonic Effects in the Optical Conductivity of Twisted Bilayer Graphene
• G band Raman double resonance in twisted bilayer graphene: an evidence of band splitting and folding
• Relaxation of Optically Excited Carriers in Graphene
• Excitonic Fano Resonance in Freestanding Graphene
• Band Topology, Orbital Phase Winding, and Selection Rules in Excitonic Physics in Two Dimensions
• Strongly bound excitons dominate electronic relaxation in resonantly excited twisted bilayer graphene
• Long valley lifetime of free carriers in monolayer WSe2
• Transient absorption and photocurrent microscopy show hot electron supercollisions describe the rate-limiting relaxation step in graphene
• Optical-phonon resonances with saddle-point excitons in twisted-bilayer graphene
• Ultrafast Spectroscopy of Mid-Infrared Internal Exciton Transitions of Separated Single-Walled Carbon Nanotubes
• New Mechanism for Strongly Bound Excitons in Gapless Two-Dimensional Structures

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• Magic Angle Hierarchy in Twisted Graphene Multilayers
• Quantum Electrodynamic Control of Matter: Cavity-Enhanced Ferroelectric Phase Transition
• Observation of Electrically Tunable van Hove Singularities in Twisted Bilayer Graphene from nanoARPES
• Symmetry of superconducting correlations in displaced bilayers of graphene
• Valley Degree of Freedom in Two-Dimensional van der Waals Materials
• High-$T_{\text{C}}$ Superconductivity Originating from Interlayer Coulomb Coupling in Gate-Charged Twisted Bilayer Graphene Moir$\acute{e}$ Superlattices
• Exciton absorption, band structure, and optical emission in biased bilayer graphene
• Moiré excitons in biased twisted bilayer graphene under pressure
• Probing the bright exciton state in twisted bilayer graphene via resonant Raman scattering
• Photon absorption in twisted bilayer graphene
• Interference effects in polarization controlled Rayleigh scattering in twisted bilayer graphene