Plasmonics in Topological Insulators: Spin–Charge Separation, the Influence of the Inversion Layer, and Phonon–Plasmon Coupling

Stauber, T.; Gómez‐Santos, G.; Brey, L.

doi:10.1021/acsphotonics.7b00524

Cited by 49 publications

(45 citation statements)

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“…In plots of both plasmon frequency as a function of wavevector (Figure 3a) and as a function of film thickness (Figure 3b www.advopticalmat.de plasmons and confirming the theory described in refs. [30,32]. In Figure 3a, the 1 µm samples seem to trend away from the theoretical curves.…”

Section: Wwwadvopticalmatdementioning

confidence: 88%

“…For constant stripe width and varying thicknesses, we see an increase in plasmon frequency with increasing thickness (consistent with a coupled 2D plasmon). [32] There is also a trend toward larger linewidths and shorter lifetimes at smaller stripe widths. The plasmon lifetime is calculated as τ pl = 1/γ pl .…”

Section: Wwwadvopticalmatdementioning

confidence: 94%

“…[34] This may be due to the plasmon hybridization with the α phonon. [32] There is also a trend toward larger linewidths and shorter lifetimes at smaller stripe widths. As the stripes become narrower, any fabrication damage along the exposed edges will have an increasingly large effect due to the higher surface:bulk ratio.…”

Section: Wwwadvopticalmatdementioning

confidence: 94%

“…The films are patterned into arrays of stripes of width W and periodicity 2W. [32] When the peak shifts to sufficiently high frequencies, most notably in Figure 1a, the α phonon reappears since the frequencies of the phonon and plasmon are sufficiently different to prohibit coupling. In Figure 1, the transverse magnetic (TM) extinction spectra for nine films of varying thicknesses and stripe widths are shown.…”

Section: Coupled Dirac Plasmons In Topological Insulatorsmentioning

confidence: 99%

“…For a constant stripe width, the extinction peak shifts to higher frequencies as film thickness increases, behavior consistent with coupled 2D Dirac plasmons. [32] When the peak shifts to sufficiently high frequencies, most notably in Figure 1a, the α phonon reappears since the frequencies of the phonon and plasmon are sufficiently different to prohibit coupling. Although the β phonon and plasmon have similar resonant frequencies in some cases, the interaction is too weak to produce a Fano lineshape.…”

Section: Coupled Dirac Plasmons In Topological Insulatorsmentioning

confidence: 99%

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Coupled Dirac Plasmons in Topological Insulators

Ginley

Law

2018

Advanced Optical Materials

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to refractive index changes, making them more efficient sensors than their noble metal counterparts in addition to reaching previously unobtainable wavelengths. [2] Unlike graphene, TSS electrons exhibit spin-momentum locking, in which the momentum of an electron determines its spin direction. The Dirac electrons are thus protected by time reversal symmetry from backscattering into other surface states in the absence of a magnetic perturbation. [12] TI plasmonics could therefore gain an advantage over graphene since the spin-momentum locking in TIs should lead to spin-polarized plasmons with long propagation distances. [5,13,14] In addition, it is straightforward to grow TI films and multilayered heterostructures on a wafer scale using molecular beam epitaxy. [15][16][17] It is important to note that although the TSSs are 2D, standard TI materials are usually 3D with 2D sheets of topologically protected Dirac electrons on each surface. Plasmon excitations in bulk TI materials have been investigated with electron energy loss spectroscopy measurements, and complex behavior attributed to both trivial surface and topological Dirac electrons has been observed. [18][19][20] Since the TI films discussed in this paper are all in the "thin film" limit of qd < 1 (where q is the wavevector of light and d is the thickness of the film), the plasmons on the top and bottom film surfaces will couple electrostatically. This results in an acoustic (dark) and an optical (bright) plasmon mode. There has been some initial work performed in this system on both the acoustic and optical plasmon modes. [21][22][23][24][25][26][27] Previous work by Di Pietro et al. [23] investigated the dependence of plasmon frequency on stripe width in etched TI films; their observations showed the expected W dependence for 2D plasmons. Though their results were consistent with Dirac plasmons, they were unable to completely rule out the possibility that they observed a 2D massive plasmon instead of the desired 2D massless plasmon.The inherently 3D nature of Bi 2 Se 3 allows for the existence of at least two carrier pathways beyond the TSS: bulk doping and a band bending two-dimensional electron gas (2DEG) at the interface of the TI and adjacent material. [28] One way to distinguish Dirac plasmons from coexisting massive bulk plasmons and massive 2DEG plasmons is by mapping how the plasmon frequency depends on film thickness as well as stripe width. Equation (1) shows the dispersion relation for massive bulk plasmons, where ω p is the plasmon frequency, e is the electron charge, n M is the 2D sheet density, ε r is the average permittivity of the surrounding materials, and q is the wavevector of light. For massive bulk plasmons, n M will increase as the film thickness increases (assuming Topological insulators are predicted to house spin-polarized 2D Dirac plasmons. In topological insulator thin films, Dirac plasmons on the top and bottom surfaces are coupled, giving rise to an unusual dispersion relationship. These plasmons are of interest both for fundam...

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Section: Wwwadvopticalmatdementioning

confidence: 88%

Section: Wwwadvopticalmatdementioning

confidence: 94%

Section: Wwwadvopticalmatdementioning

confidence: 94%

Section: Coupled Dirac Plasmons In Topological Insulatorsmentioning

confidence: 99%

Section: Coupled Dirac Plasmons In Topological Insulatorsmentioning

confidence: 99%

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Coupled Dirac Plasmons in Topological Insulators

Ginley

Law

2018

Advanced Optical Materials

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Dirac Fermion and Plasmon Dynamics in Graphene and 3D Topological Insulators

Choi

2019

Advanced Optical Materials

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Light–matter interactions illuminate the nature of solids and provide a second look on associated carrier dynamics. In particular, graphene and 3D topological insulators (3D TI) with broadband electromagnetic excitation have revealed to host exotic dynamic interactions. Much of Dirac‐point physics arises from discrete lattice symmetries and nontrivial Z2 classification of Bloch states. In this review, ongoing spectroscopic works on graphene and 3D TI are presented, where special attention is on the far‐infrared terahertz (THz) spectroscopy that characterizes the intraband dynamics. The constant absorbance of graphene upon interband particle–hole generation exhibits nonclassical results of gapless dispersion, which can be elucidated by the relativistic Dirac equations with zero rest mass. The massless Dirac fermions on graphene and 3D TI surface exhibit distinct phenomena compared to the conventional systems. First, the transient responses after pulse excitation reveal the semimetallic states of the gapless electronic dispersion, where the Fermi energy in equilibrium determines the crossover from metallic to semiconducting states. Second, the 2D Dirac plasmon dispersion of graphene and 3D TI surface exhibits unconventional density dependence in comparison to the massive electronic systems. The novel optical phenomena in graphene and 3D TI surface can serve for advanced optoelectronic and optospintronic applications.

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Inverse design of topological metaplates for flexural waves with machine learning

Wen

Jin

et al. 2021

Materials & Design

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Plasmonics in Topological Insulators: Spin–Charge Separation, the Influence of the Inversion Layer, and Phonon–Plasmon Coupling

Cited by 49 publications

References 71 publications

Coupled Dirac Plasmons in Topological Insulators

Coupled Dirac Plasmons in Topological Insulators

Dirac Fermion and Plasmon Dynamics in Graphene and 3D Topological Insulators

Inverse design of topological metaplates for flexural waves with machine learning

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