Observation of Magnetoplasmons in Bi<sub>2</sub>Se<sub>3</sub> Topological Insulator

Autore, Marta; Engelkamp, Hans; D’Apuzzo, Fausto; Gaspare, Alessandra Di; Pietro, P. Di; Vecchia, I. Lo; Brahlek, Matthew; Koirala, Nikesh; Oh, Seongshik; Lupi, S.

doi:10.1021/acsphotonics.5b00036

Cited by 52 publications

(65 citation statements)

References 26 publications

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“…If true, BSTS or other TIs would be a radically new material platform for broadband nanoplasmonic devices that can be modulated optically, 16 through injection of electrons, 17 or by applied magnetic fields. 18 In this work, we use density functional theory (DFT) calculations to investigate the electronic band structures and optical properties of seven compounds in the Bi x Sb 1-x Te y Se 1-y (BSTS) family of TIs, in bulk crystal and thin film forms, with the overall goal of determining their suitability for nanoplasmonics (similar ab-initio studies have proven effective with metals, [19][20][21] alkali-noble intermetallics 22 and galliumdoped zinc oxide 23 ). Our results show that plasmonic behavior of quaternary trichalcogenide compounds in the optical part of the spectrum has three origins: (a) bulk interband transitions contributing primarily in the visible spectral region; (b) intraband transition within topologically protected surface bands contributing in the mid-infrared region; (c) interband transition between topologically protected surface states and bulk states, dominating in the UV-near-infrared (NIR) range.…”

Section: Introductionmentioning

confidence: 99%

Plasmonics of topological insulators at optical frequencies

et al. 2017

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The development of nanoplasmonic devices, such as plasmonic circuits and metamaterial superlenses in the visible to ultraviolet frequency range, is hampered by the lack of low-loss plasmonic media. Recently, strong plasmonic response was reported in a certain class of topological insulators. Here, we present a first-principles density functional theory analysis of the dielectric functions of topologically insulating quaternary (Bi,Sb) 2 (Te,Se) 3 trichalcogenide compounds. Bulk plasmonic properties, dominated by interband transitions, are observed from 2 to 3 eV and extend to higher frequencies. Moreover, trichalcogenide compounds are better plasmonic media than gold and silver at blue and UV wavelengths. By analyzing thin slabs, we also show that these materials exhibit topologically protected surface states, which are capable of supporting propagating plasmon polariton modes over an extremely broad spectral range, from the visible to the mid-infrared and beyond, owing to a combination of interand intra-surface band transitions. NPG Asia Materials (2017) 9, e425; doi:10.1038/am.2017.149; published online 25 August 2017 INTRODUCTIONThe fields of metamaterials and plasmonics have seen an extraordinary evolution in recent years, from the initial theoretical predictions of artificial negative refractive indices and cloaking 1,2 to the experimental realization of photonic metadevices with various functionalities that can be engineered and obtained on demand. 3,4 However, the practical implementations of plasmonic and metamaterial devices have long been hampered by energy dissipation in plasmonic media, especially in the visible to ultraviolet (UV) range, where even the best plasmonic metals (such as gold, silver and aluminum) suffer from strong dissipation due to interband electronic transitions and Drude losses. 5 This has inspired a search for alternative low-loss plasmonic materials for optical devices operating at high frequencies. 6,7 Candidates that are currently being investigated include highly doped semiconductors, metallic alloys, nitrides and oxides 8 and, more recently, twodimensional materials and topological insulator (TI) materials.TIs represent a new quantum phase of matter, which originates from the topological character of the bulk electronic bands in certain materials. The strong spin-orbit coupling in such materials leads to a band inversion and the appearance of Dirac surface states in the band gap. These topological surface states are chiral and protected from back-scattering by time-reversal symmetry. As a consequence, charge carriers from topologically protected surface states can carry current and are free to move parallel to the surface. Thus, TIs are ideal candidates to realize exotic plasmonic phenomena. Localized plasmons have recently been observed in TIs at THz frequencies (in Bi 2 Se 3 ) 9,10 as well as visible-to-UV frequencies (in single crystal

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Section: Introductionmentioning

confidence: 99%

Plasmonics of topological insulators at optical frequencies

et al. 2017

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“…In micro- and nano- ordered structures based on conventional metals and 2D electron gas systems35242526272829, the plasmon frequency depends on both the charge-carrier density and the geometrical parameters of the structure. In a disordered system one still expects a dependence on these parameters, although disorder may affect both the plasmon frequency, linewidth and intensity30.…”

Section: Discussionmentioning

confidence: 99%

Terahertz and mid-infrared plasmons in three-dimensional nanoporous graphene

et al. 2017

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Two-dimensional (2D) graphene emerged as an outstanding material for plasmonic and photonic applications due to its charge-density tunability, high electron mobility, optical transparency and mechanical flexibility. Recently, novel fabrication processes have realised a three-dimensional (3D) nanoporous configuration of high-quality monolayer graphene which provides a third dimension to this material. In this work, we investigate the optical behaviour of nanoporous graphene by means of terahertz and infrared spectroscopy. We reveal the presence of intrinsic 2D Dirac plasmons in 3D nanoporous graphene disclosing strong plasmonic absorptions tunable from terahertz to mid-infrared via controllable doping level and porosity. In the far-field the spectral width of these absorptions is large enough to cover most of the mid-Infrared fingerprint region with a single plasmon excitation. The enhanced surface area of nanoporous structures combined with their broad band plasmon absorption could pave the way for novel and competitive nanoporous-graphene based plasmonic-sensors.

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“…We note immediately that if we take only the modes at l = 0, the dependence on the angular part disappears in Eq. (15). Therefore, for the modes at l = 0, there are only longitudinal and transverse components of the field, while, for modes with l different from zero, also the angular component E φ appears.…”

Section: Dynamic Structure Factormentioning

confidence: 93%

“…Only recently, Dirac magneto-plasmons were observed in TI showing high frequency tunability in the mid-infrared and terahertz spectral regions [14][15][16][17][18] . Due to the spin-momentum locking 19,20 , these plasmons are always coupled to spin waves acquiring a spin character.…”

Section: Introductionmentioning

confidence: 99%

Plasmons in topological insulator cylindrical nanowires

2017

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We present a theoretical analysis of Dirac magneto-plasmons in topological insulator nanowires. We discuss a cylindrical geometry where Berry phase effects induce the opening of a gap at the neutrality point. By taking into account surface electron wave functions introduced in previous papers and within the random phase approximation, we provide an analytical form of the dynamic structure factor. Dispersions and spectral weights of Dirac plasmons are studied with varying the radius of the cylinder, the surface doping, and the strength of an external magnetic field. We show that, at zero surface doping, inter-band damped plasmon-like excitations form at the surface and survive at low electron surface dopings (∼ 10 10 cm −2 ). Then, we point out that the plasmon excitations are sensitive to the Berry phase gap closure when an external magnetic field close to half quantum flux is introduced. Indeed, a well-defined magneto-plasmon peak is observed at lower energies upon the application of the magnetic field. Finally, the increase of the surface doping induces a crossover from damped inter-band to sharp intra-band magneto-plasmons which, as expected for large radii and dopings (∼ 10 12 cm −2 ), approach the proper limit of a two-dimensional surface.

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Observation of Magnetoplasmons in Bi₂Se₃ Topological Insulator

Cited by 52 publications

References 26 publications

Plasmonics of topological insulators at optical frequencies

Plasmonics of topological insulators at optical frequencies

Terahertz and mid-infrared plasmons in three-dimensional nanoporous graphene

Plasmons in topological insulator cylindrical nanowires

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Observation of Magnetoplasmons in Bi2Se3 Topological Insulator

Cited by 52 publications

References 26 publications

Plasmonics of topological insulators at optical frequencies

Plasmonics of topological insulators at optical frequencies

Terahertz and mid-infrared plasmons in three-dimensional nanoporous graphene

Plasmons in topological insulator cylindrical nanowires

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Observation of Magnetoplasmons in Bi₂Se₃ Topological Insulator