Planar Hall effect from the surface of topological insulators

A prominent feature of topological insulators (TIs) is the surface states comprising of spin-nondegenerate massless Dirac fermions. Recent technical advances have made it possible to address the surface transport properties of TI thin films by tuning the Fermi levels of both top and bottom surfaces. Here we report our discovery of a novel planar Hall effect (PHE) from the TI surface, which results from a hitherto-unknown resistivity anisotropy induced by an in-plane magnetic field. This effect is observed in dual-gated devices of bulk-insulating Bi2−x Sb x Te3 thin films, where the field-induced anisotropy presents a strong dependence on the gate voltage with a characteristic two-peak structure near the Dirac point. The origin of PHE is the peculiar time-reversal-breaking effect of an in-plane magnetic field, which anisotropically lifts the protection of surface Dirac fermions from backscattering. The observed PHE provides a useful tool to analyze and manipulate the topological protection of the TI surface

Plasmonic properties and photoinduced reflectance of topological insulator

We report on linear and nonlinear infrared and plasmonic properties of chalcogenide crystal of the Bi-Sb-Te-Se family that was recently identified as a prospective platform for switchable broadband plasmonic devices

UV & visible plasmonic metamaterials made of topological insulator

Plasmonic resonances are observed in metamaterials made of a topological insulator, Bi1.5Sb0.5Te1.8Se1.2, at the UV and visible frequencies due to the material’s interband transition and nontrivial surface conducting state

Near-field detection of plasmonic modes in topological insulator nanostructures in the visible part of the spectrum

In this work we perform direct nano-imaging of nanostructured Bi1.5Sb0.5Te1.8Se1.2 (BSTS) topological insulator in the visible range and show the evidence of dipolar and higher order local surface plasmon modes. Revealed plasmon modes in BSTS nanostructures present the TI as a good plasmonic material beyond noble metals

Ultraviolet and visible plasmonic metamaterials made of topological insulator

We provide the first demonstration of plasmonic metamaterials made of a semiconducting material, Bi1.5Sb0.5Te1.8Se1.2 (BSTS), which is also known as a topological insulator, working at the UV and visible frequencies where finding a good plasmonic material is extremely challenging. Spectroscopic ellipsometry of the material revealed the existence of negative permittivity in the wavelengths 200 – 670 nm, which is rarely seen at the first absorption edge of semiconductors in nature. The negative permittivity is attributed to the combination of bulk interband transitions and surface contribution of the topologically protected states. Metamaterials fabricated from the BSTS crystal show plasmonic resonances from 350 nm to 550 nm while surface gratings exhibit cathodoluminescence peaks from 230 nm to 1050 nm. This finding of new class of materials with high-frequency plasmonic response could advance plasmonics in view of merging plasmonic functionality with electronics thanks to the nature of the material

Plasmonics of topological insulators at UV-visible frequencies

We report the first observation of the plasmonic behavior of a semiconducting material, Bi1.5Sb0.5Te1.8Se1.2, at the UV and visible frequencies, which was revealed by spectroscopic ellipsometry, reflection and cathodoluminescence measurements. Its plasmonic response originates from the negative dielectric permittivity at the material’s first absorption edge, which is rarely seen in nature, together with the contribution of the nontrivial surface conducting states of the material

Технологія відпрацювання тонких пластів із закладкою виробленого простору

The monograph concerns substantiation of basic parameters and application area of thin coal seam mining with the worked-out area stowing by means of undercut rocks. As a result of the studies, regularities of changes in stress-strain state of rock mass depending upon operational parameters of mining procedures while the worked-out area stowing. The opportunity to use rocks of Western Donbas as stowing material has been substantiated. Basic design features of winning-stowing systems have been determined; operation schedules to mine thin seams with stowing for mines in Western Donbas have been developed. The monograph is meant for students, engineers and technicians, academics, scientific-research institutes, and project organizations of coal industry

Ultrathin BaTiO3-Based Ferroelectric Tunnel Junctions through Interface Engineering

10.1021/acs.nanolett.5b00138Nano Letters1542568-257

Experimental evidences of topological surface states of β-Ag 2Te

10.1063/1.4795735AIP Advances33