7,633 research outputs found
Topological superconductivity at the edge of transition metal dichalcogenides
Time-reversal breaking topological superconductors are new states of matter
which can support Majorana zero modes at the edge. In this paper, we propose a
new realization of one-dimensional topological superconductivity and Majorana
zero modes. The proposed system consists of a monolayer of transition metal
dichalcogenides MX2 (M=Mo, W; X=S, Se) on top of a superconducting substrate.
Based on first-principles calculations, we show that a zigzag edge of the
monolayer MX2 terminated by metal atom M has edge states with strong spin-orbit
coupling and spontaneous magnetization. By proximity coupling with a
superconducting substrate, topological superconductivity can be induced at such
an edge. We propose NbS2 as a natural choice of substrate, and estimate the
proximity induced superconducting gap based on first-principles calculation and
low energy effective model. As an experimental consequence of our theory, we
predict that Majorana zero modes can be detected at the 120 degree corner of a
MX2 flake in proximity with a superconducting substrate
An optical fiber tip micrograting thermometer
An ~12 µm long Bragg grating was engraved in an ~5 µm diameter optical fiber tip by focused ion beam (FIB) milling. An ~10-dB extinction was achieved at 1570 nm with only 11 indentations. The grating was used for temperature sensing, and it exhibited a temperature sensitivity of ~22 pm/°C
Large-gap quantum spin Hall insulators in tin films
The search of large-gap quantum spin Hall (QSH) insulators and effective
approaches to tune QSH states is important for both fundamental and practical
interests. Based on first-principles calculations we find two-dimensional tin
films are QSH insulators with sizable bulk gaps of 0.3 eV, sufficiently large
for practical applications at room temperature. These QSH states can be
effectively tuned by chemical functionalization and by external strain. The
mechanism for the QSH effect in this system is band inversion at the \Gamma
point, similar to the case of HgTe quantum well. With surface doping of
magnetic elements, the quantum anomalous Hall effect could also be realized
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