Intrinsically undamped plasmon modes in narrow electron bands

Lewandowski, Cyprian; Levitov, Leonid

doi:10.1073/pnas.1909069116

Cited by 68 publications

(58 citation statements)

References 38 publications

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“…Examples of the latter are hyperbolic and chiral polaritonics, using 2D polaritons for controlling the dynamics of emitters placed in the vicinity of a 2D material, or the engineering of new flavors of polaritons (e.g., plasmon–exciton polaritons, plasmon–phonon polaritons, etc.). Other alluring research directions are 2D material‐based topological photonics, twist‐polaritonics, as well as transdimensional photonics (i.e., the intermediate regime between the “strictly 3D” and the “strictly 2D” regime).…”

Section: Discussionmentioning

confidence: 99%

Strong Light–Matter Interactions Enabled by Polaritons in Atomically Thin Materials

Gonçalves

Stenger

Cox

et al. 2020

Advanced Optical Materials

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Polaritons, resulting from the hybridization of light with polarization charges formed at the boundaries between media with positive and negative dielectric response functions, can focus light into regions much smaller than its associated free‐space wavelength. This property is paramount for a plethora of applications in nanophotonics, ranging from biological sensing to photocatalysis to nonlinear and quantum optics. In the two‐dimensional (2D) limit, represented by atomically thin and van der Waals (vdW) materials of single‐layers bound by weak vdW attraction, polaritons are characterized by extremely small wavelengths associated with extreme optical confinement, and furthermore can exhibit long lifetimes, electrical tunability, and extreme sensitivity to their dielectric environment, among many other desirable qualities in nano‐optical device applications. Here, the fundamentals of polaritons in atomically thin materials are summarized, emphasizing plasmon and exciton polaritons, their strong light–matter interactions, and nonlinear plasmonics. More specifically, this review opens with a pedagogical discussion of plasmons in extended and nanostructured graphene, providing a classical electrodynamical model in a nonretarded theoretical framework, and the ultraconfined acoustic plasmons supported by hybrid graphene–dielectric–metal structures. In addition, the basic principles are introduced and the recent developments on nonlinear graphene plasmonics and on strong coupling physics with atomically thin transition metal dichalcogenides are reviewed. Finally, potentially new, promising research directions in the burgeoning field of 2D nanophotonics are identified.

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Section: Discussionmentioning

confidence: 99%

Strong Light–Matter Interactions Enabled by Polaritons in Atomically Thin Materials

Gonçalves

Stenger

Cox

et al. 2020

Advanced Optical Materials

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“…The calculation in Fig. 1 describes as well the plasmons of the system ( 38 ). Further results concerning the plasmon spectrum are reported in SI Appendix , section 2 .…”

Section: The Modelmentioning

confidence: 98%

“…This figure measures the density of charge density excitations, weighted by their coupling to the electron quasiparticles. The lower horizontal bright bands show the electron–hole continuum, the bands directly above them are the plasmons ( 38 ), and the faint blue lines give the renormalized plasmons, broadened by their interaction with the electron–hole continuum.…”

Section: The Modelmentioning

confidence: 99%

“…The calculation is based on the Kohn–Luttinger formalism ( 36 ) for the study of anisotropic superconductivity via repulsive interactions. The screening includes electron–hole pairs ( 37 ), plasmons ( 38 ), and phonons (note that acoustic phonons overlap with the electron–hole continuum in TBG). Our results show that the repulsive Coulomb interaction, screened by plasmons and electron–hole pairs only, leads to anisotropic superconductivity, although with critical temperatures of order T c ∼ 10 −3 to 10 −2 K. The inclusion of phonons in the screening function substantially enhances the critical temperature, to T c ∼ 1 to 10 K.…”

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confidence: 99%

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Coulomb interaction, phonons, and superconductivity in twisted bilayer graphene

Cea

Guinea

2021

Proc. Natl. Acad. Sci. U.S.A.

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The polarizability of twisted bilayer graphene, due to the combined effect of electron–hole pairs, plasmons, and acoustic phonons, is analyzed. The screened Coulomb interaction allows for the formation of Cooper pairs and superconductivity in a significant range of twist angles and fillings. The tendency toward superconductivity is enhanced by the coupling between longitudinal phonons and electron–hole pairs. Scattering processes involving large momentum transfers, Umklapp processes, play a crucial role in the formation of Cooper pairs. The magnitude of the superconducting gap changes among the different pockets of the Fermi surface.

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“…Also collective modes in twisted structures have been studied and show several new features [13][14][15][16][17][18][19][20][21][22][23]. In this Letter, however, we will discuss the collective excitations associated with the network of chiral electronic edge states (EES) that appear when an electric field is applied perpendicular to the sample and the chemical potential lies inside the gap [24][25][26].…”

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confidence: 99%

Plasmonic Dirac Cone in Twisted Bilayer Graphene

et al. 2020

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We discuss plasmons of biased twisted bilayer graphene when the Fermi level lies inside the gap. The collective excitations are a network of chiral edge plasmons (CEP) entirely composed of excitations in the topological electronic edge states that appear at the AB-BA interfaces. The CEP form a hexagonal network with a unique energy scale ϵ p ¼ ðe 2 Þ=ðϵ 0 ϵt 0 Þ with t 0 the moiré lattice constant and ϵ the dielectric constant. From the dielectric matrix we obtain the plasmon spectra that has two main characteristics: (i) a diverging density of states at zero energy, and (ii) the presence of a plasmonic Dirac cone at ℏω ∼ ϵ p =2 with sound velocity v D ¼ 0.0075c, which is formed by zigzag and armchair current oscillations. A network model reveals that the antisymmetry of the plasmon bands implies that CEP scatter at the hexagon vertices maximally in the deflected chiral outgoing directions, with a current ratio of 4=9 into each of the deflected directions and 1=9 into the forward one. We show that scanning near-field microscopy should be able to observe the predicted plasmonic Dirac cone and its broken symmetry phases.

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Intrinsically undamped plasmon modes in narrow electron bands

Cited by 68 publications

References 38 publications

Strong Light–Matter Interactions Enabled by Polaritons in Atomically Thin Materials

Strong Light–Matter Interactions Enabled by Polaritons in Atomically Thin Materials

Coulomb interaction, phonons, and superconductivity in twisted bilayer graphene

Plasmonic Dirac Cone in Twisted Bilayer Graphene

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