Experimentalists have observed the predicted half-integer quantum Hall effect using the topological insulator BiSbTeSe2, which exhibits topological surface states at room temperature, with each surface contributing a half quantum of Hall conductance.

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Observation of topological surface state quantum Hall effect in an intrinsic three-dimensional topological insulator

https://iopscience.iop.org/article/10.1088/2053-1583/aaf836/pdf

A roadmap for electronic grade 2D materials

Caracterisation optique et physique de ZnSe. Etude des macles et des deformations thermoelastiques d'une couche ZnSe sur un substrat. Etude des excitons libres dans des films de ZnSe, des impuretes et defauts dans la couche de ZnSe epitaxique, et de leurs proprietes optiques non lineaires

Optical Properties of ZnSe Epilayers and Films

We describe a reproducible method of fabricating adiabatic tapers with 3–4μm diameter. The method is based on a heat-and-pull rig, whereby a CO2 laser is continuously scanned across a length of fiber that is being pulled synchronously. Our system relies on a CO2 mirror mounted on a geared stepper motor in order to scan the laser beam across the taper region. We show that this system offers a reliable alternative to more traditional rigs incorporating galvanometer scanners. We have routinely obtained transmission losses between 0.1 and 0.3dB indicating the satisfactory production of adiabatic tapers. The operation of the rig is described in detail and an analysis on the produced tapers is provided. The flexibility of the rig is demonstrated by fabricating prolate dielectric microresonators using a microtapering technique. Such a rig is of interest to a range of fields that require tapered fiber fabrication such as microcavity-taper coupling, atom guiding along a tapered fiber, optical fiber sensing, and th...

An inexpensive heat-and-pull rig for fiber taper fabrication

Using angle-resolved photoemission spectroscopy, we report electronic structure for representative members of ternary topological insulators. We show that several members of this family, such as Bi2Se2Te, Bi2Te2Se, and GeBi2Te4, exhibit a singly degenerate Dirac-like surface state, while Bi2Se2S is a fully gapped insulator with no measurable surface state. One of these compounds, Bi2Se2Te, shows tunable surface state dispersion upon its electronic alloying with Sb (SbxBi2-xSe2Te series). Other members of the ternary family such as GeBi2Te4 and BiTe1.5S1.5 show an in-gap surface Dirac point, the former of which has been predicted to show nonzero weak topological invariants such as (1;111); thus belonging to a different topological class than BiTe1.5S1.5. The measured band structure presented here will be a valuable guide for interpreting transport, thermoelectric, and thermopower measurements on these compounds. The unique surface band topology observed in these compounds contributes towards identifying designer materials with desired flexibility needed for thermoelectric and spintronic device fabrication.

Topological surface states and Dirac point tuning in ternary topological insulators

Growth of Bi2Te3 films and other phases of Bi-Te system by MOVPE

Metalorganic vapor phase epitaxy growth of ternary tetradymite Bi2Te3−xSex compounds

Optimization of growth conditions allows us to grow mirror-like hexagonal ZnCdS layers and CdSSe/ZnCdS quantum well (QW) structures on CdS(0001) and ZnCdS(0001) substrates by MOVPE. ZnCdS epilayers with high cathodoluminescence (CL) intensity at room temperature (RT) have also been obtained. An intense QW emission line has been observed in CdS/ZnCdS QW structures. With increasing excitation intensity the line shifted to shorter wavelength, which is a manifestation of an internal piezoelectric effect. An additional short-wavelength line appears in low-temperature CL spectra of CdSSe/ZnCdS QW structures due to localization of charge carriers by nonuniformity of alloy composition or QW thickness.

G. G. Yakushcheva

Papers

Growth of Bi2Te3 films and other phases of Bi-Te system by MOVPE

Metalorganic vapor phase epitaxy growth of ternary tetradymite Bi2Te3−xSex compounds

Hexagonal ZnCdS epilayers and CdSSe/ZnCdS QW structures on CdS(0001) and ZnCdS(0001) substrates grown by MOVPE

MOVPE deposition of Sb 2 Te 3 and other phases of Sb-Te system on sapphire substrate

Transmission spectrum alteration of a silica fiber taper while covering lateral surface with heterostructure of ZnTe/Bi2Te3 thin film