Observation of Bulk and Edge Magnetoplasmons in a Two-Dimensional Electron Fluid

Mast, David; Dahm, A. J.; Fetter, Alexander L.

doi:10.1103/physrevlett.54.1706

Cited by 287 publications

(156 citation statements)

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“…Unlike metal plasmons 19 , the graphene plasmon is expected to be strongly affected by an external magnetic field due to a comparable cyclotron frequency [20][21][22] and plasmon frequency. The effects of a perpendicular magnetic field on the plasmons in conventional 2DEG systems have been extensively studied [7][8][9][10][11]17,23,24 . A major focus of these studies has been localized plasmons in disks 7 and submicron size quantum dots 8,17,23 .…”

Section: Main Textmentioning

confidence: 99%

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Infrared Spectroscopy of Tunable Dirac Terahertz Magneto-Plasmons in Graphene

et al. 2012

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Abstract:Boundaries and edges of a two dimensional system lower its symmetry and are usually regarded, from the point of view of charge transport, as imperfections. Here we present a first study of the behavior of graphene plasmons 1-6 in a strong magnetic field that provides a different perspective. We show that the plasmon resonance in micron size graphene disks 4,6 in a strong magnetic field splits into edge and bulk plasmon modes 7-12 with opposite dispersion relations, and that the edge plasmons at terahertz frequencies develop increasingly longer lifetimes with increasing magnetic field, in spite of potentially more defects close to the graphene edges. This unintuitive behavior is attributed to increasing quasi-one dimensional field-induced confinement and the resulting suppression of the back-scattering 13 .Due to the linear band structure of graphene 14,15 , the splitting rate of the edge and bulk modes develops a strong doping dependence, which differs from the behavior of traditional semiconductor two-dimensional electron gas (2DEG) systems 7,8,11,16 .We also observe the appearance of a higher order mode indicating an anharmonic confinement potential 17 even in these well-defined circular disks. Our work not only 2 opens an avenue for studying the physics of graphene edges, but also supports the great potential of graphene for tunable terahertz magneto-optical devices. Main text:Plasmon excitations in graphene are currently attracting great attention [1][2][3][4][5][6]12 . This is primarily due to the high carrier mobility and the tunable carrier density, which make graphene a promising plasmonic material in the far infrared and terahertz frequency ranges 1,2,5,6,18 . Unlike metal plasmons 19 , the graphene plasmon is expected to be strongly affected by an external magnetic field due to a comparable cyclotron frequency 20-22 and plasmon frequency. The effects of a perpendicular magnetic field on the plasmons in conventional 2DEG systems have been extensively studied [7][8][9][10][11]17,23,24 . A major focus of these studies has been localized plasmons in disks 7 and submicron size quantum dots 8,17,23 .Here we report the first study of magneto-plasmons in micron size disk arrays of graphene-a different kind two dimensional system. We find that the plasmon lifetime can be dramatically modified by a magnetic field. This is especially true for the edge mode, which develops a much longer lifetime than that at zero field. This behavior is counterintuitive since imperfections of the edges may introduce more scattering and decrease the plasmon lifetime. To the best of our knowledge, this is the first demonstration of magnetic field tuning of plasmon lifetime in the terahertz frequency range.Large area graphene disk arrays on SiO 2 /Si are fabricated using standard electron beam lithography and dry etching techniques (for details, see Methods) 6 . Fig. 1a shows a 3 scanning electron micrograph of a sample with a 3-micron diameter (d = 3 m) disk array arranged in a triangular lattice, where the lattice constan...

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Section: Main Textmentioning

confidence: 99%

“…This mode is the socalled edge magneto-plasmon 9 . It features a current along the edge and hence a rotating dipole with frequency ω -.…”

Section: Main Textmentioning

confidence: 99%

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Infrared Spectroscopy of Tunable Dirac Terahertz Magneto-Plasmons in Graphene

et al. 2012

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“…The field-induced splitting of the plasmon peak resembles strikingly the appearance of collective resonances observed previously in disk-shaped quantum dots of two-dimensional electron gases based on GaAs heterostructures 17,19 and in bound 2D electrons on the surface of liquid helium. 29,30 In both cases, the upper and lower branches were attributed to the so-called bulk and edge magnetoplasmons, respectively, with the frequencies 17…”

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confidence: 96%

Intrinsic Terahertz Plasmons and Magnetoplasmons in Large Scale Monolayer Graphene

et al. 2012

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We show that in graphene epitaxially grown on SiC the Drude absorption is transformed into a strong terahertz plasmonic peak due to natural nanoscale inhomogeneities, such as substrate terraces and wrinkles. The excitation of the plasmon modifies dramatically the magneto-optical response and in particular the Faraday rotation. This makes graphene a unique playground for plasmon-controlled magneto-optical phenomena thanks to a cyclotron mass 2 orders of magnitude smaller than in conventional plasmonic materials such as noble metals.

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“…In addition to the regular bulk plasmons, 1,2 a finite twodimensional electron gas (2DEG) such as a semi-infinite half-plane [3][4][5][6] or a finite disk, [7][8][9][10] supports edge plasmons or perimeter waves that are localized at the boundary of the two-dimensional (2D) system. 11 Xia and Quinn showed that systems with gradual edge density profiles support several types of edge waves (multipole modes) 12 that can be thought of as standing-wave plasmons fitting into the diffuse edge layer.…”

Section: Introductionmentioning

confidence: 99%

Edge plasmons in graphene nanostructures

2011

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Plasmon modes in graphene are influenced by the unusual dispersion relation of the material. For bulk plasmons this results in a n 1/4 dependence of the plasma frequency on the charge density, as opposed to the n 1/2 dependence in two-dimensional electron gas (2DEG); yet, bulk plasmon dispersion in graphene follows a similar q 1/2 behavior as for other two-dimensional materials. In this work we consider finite graphene nanostructures, semi-infinite sheets, and circular disks and study edge plasmons that are confined to the boundaries of the structures. We find that, for abrupt edges, graphene edge plasmons behave analogously to those in 2DEGs, but, for gradual edge profiles, important distinctions arise. In particular, we show that for a linear edge profile, graphene supports fewer edge modes than a 2DEG at a given q, and the edge monopole plasmon dispersion in graphene follows a q 1/4 law in contrast to the q 0 behavior seen in 2DEGs.

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Observation of Bulk and Edge Magnetoplasmons in a Two-Dimensional Electron Fluid

Cited by 287 publications

References 8 publications

Infrared Spectroscopy of Tunable Dirac Terahertz Magneto-Plasmons in Graphene

Infrared Spectroscopy of Tunable Dirac Terahertz Magneto-Plasmons in Graphene

Intrinsic Terahertz Plasmons and Magnetoplasmons in Large Scale Monolayer Graphene

Edge plasmons in graphene nanostructures

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