Ultraviolet and visible range plasmonics in the topological insulator Bi1.5Sb0.5Te1.8Se1.2

Abstract

The development of metamaterials, data processing circuits and sensors for the visible and ultraviolet parts of the spectrum is hampered by the lack of low-loss media supporting plasmonic excitations. This has driven the intense search for plasmonic materials beyond noble metals. Here we show that the semiconductor Bi 1.5 Sb 0.5 Te 1.8 Se 1.2 , also known as a topological insulator, is also a good plasmonic material in the blue-ultraviolet range, in addition to the already-investigated terahertz frequency range. Metamaterials fabricated from Bi 1.5 Sb 0.5 Te 1.8 Se 1.2 show plasmonic resonances from 350 to 550 nm, while surface gratings exhibit cathodoluminescent peaks from 230 to 1,050 nm. The observed plasmonic response is attributed to the combination of bulk charge carriers from interband transitions and surface charge carriers of the topological insulator. The importance of our result is in the identification of new mechanisms of negative permittivity in semiconductors where visible range plasmonics can be directly integrated with electronics.

Nano-optomechanical nonlinear dielectric metamaterials

“…Non-metallic metamaterial nanostructures currently attract intense attention as they promise to reduce the losses and costs associated with the use of noble metals in traditional plasmonic architectures. 1 It has already been shown that oxides and nitrides, 2 graphene, 3 topological insulators, 4 and high-index dielectrics [5][6][7][8][9][10][11][12][13] can be used as platforms for the realization of high-Q resonant metamaterials. A variety of non-metallic media, such as graphene, 14 carbon nanotubes, 15 liquid crystals, 16 and semiconductors, 17,18 have also been engaged through hybridization with plasmonic metamaterials to create media with strongly enhanced optical nonlinearities, while a nano-optomechanical nonlinearity has recently been observed in a plasmonic metamaterial.…”

Plasmons in topological insulator cylindrical nanowires

“…In Section 6, the short lifetimes of inter-band plasmon-like excitations will be compared with long ones of intra-band plasmons. In this section, considering the chemical potential in gap (µ = 0 < ∆), we need only to analyze the contribution −χ − ∞ of the equation (17). Moreover, the l = 0 contribution to the susceptibility come only from interband transitions associated to the same sub-band number m but opposite s in Eq.…”

“…In order to find the dispersion and spectral weight associated with the plasmon excitations, we have to consider all three contributions of equation (17). We start analyzing the case of low electron doping to understand how the crossover between inter-and intra-band plasmon takes place.…”

“…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.…”

Metamaterials at the University of Southampton and beyond

“…At NTU, we are exploring the use of new materials for metamaterials, such as topological insulators [138,139] and perovskites [140], as well as studying the quantum effects of light interaction with metamaterials. In 2015 we demonstrated a quantum metamaterial based on the hybridization of plasmonic landscapes with atomic gas [141].…”