12,718 research outputs found
High quality epitaxial ZnSe and the relationship between electron mobility and photoluminescence characteristics
High quality epitaxial layers of nominally undoped ZnSe have been grown by metalorganic chemical vapor deposition at low temperature (325â°C) and pressure (30 Torr), using dimethylzinc and hydrogen selenide. All layers were unintentionally doped n type with net carrier concentrations of 6.4Ă10^(14)â1.5Ă10^(16) cm^(â3) and exhibited very high mobility at room temperature (up to 500 cm2/Vâs) as well as at 77 K, where the measured value of 9250 cm^2/Vâs is the highest so far reported for vapor phase growth. Additional evidence for the high quality of the material is provided by photoluminescence. Experimental results indicate a correlation between the photoluminescence characteristics and the electrical properties that may be useful in assessing the quality of ZnSe films
Probing WIMPs in space-based gravitational wave experiments
Although searches for dark matter have lasted for decades, no convincing
signal has been found without ambiguity in underground detections, cosmic ray
observations, and collider experiments. We show by example that gravitational
wave (GW) observations can be a supplement to dark matter detections if the
production of dark matter follows a strong first-order cosmological phase
transition. We explore this possibility in a complex singlet extension of the
standard model with CP symmetry. We demonstrate three benchmarks in which the
GW signals from the first-order phase transition are loud enough for future
space-based GW observations, for example, BBO, U-DECIGO, LISA, Taiji, and
TianQin. While satisfying the constraints from the XENON1T experiment and the
Fermi-LAT gamma-ray observations, the dark matter candidate with its mass
around ~TeV in these scenarios has a correct relic abundance obtained
by the Planck observations of the cosmic microwave background radiation.Comment: 11 pages, 2 figures, 2 table
IMAGE-BASED MEASUREMENT AND BIOMECHANICAL ANALYSIS OF THE KNEE JOINT DURING FUNCTIONAL ACTIVITIES
A new approach based on the integration of medical image-based measurement techniques, infrared stereophotogrammetry and finite element modelling (FEM) was developed for comprehensive subject-specific biomechanical analyses of the knee joint during weight-bearing functional activities including cycling. The medical image-based methods include digitally reconstructed radiograph (DRR) based 3D fluoroscopy methods, and a new slice-to-volume registration method using FLASH MRI for the real-time measurement of the 3D kinematics of the knee in vivo. With the new approach, the soft tissue artefacts associated with skin marker-based stereophotogrammetry and their effects on the calculated biomechanical variables were also investigated
Intrinsic topological superconductivity with exactly flat surface bands in the quasi-one-dimensional ACrAs (A=Na, K, Rb, Cs) superconductors
A spin-U(1)-symmetry protected momentum-dependent integer--valued
topological invariant is proposed to time-reversal-invariant (TRI)
superconductivity (SC) whose nonzero value will lead to exactly flat surface
band(s). The theory is applied to the weakly spin-orbit coupled quasi-1D
ACrAs (A=Na, K, Rb, Cs) superconductors family with highest
up to 8.6 K with -wave pairing in the channel. It's found that up
to the leading atomic spin-orbit-coupling (SOC), the whole (001) surface
Brillouin zone is covered with exactly-flat surface bands, with some regime
hosting three flat bands and the remaining part hosting two. Such exactly-flat
surface bands will lead to very sharp zero-bias conductance peak in the
scanning tunneling microscopic spectrum. When a tiny subleading spin-flipping
SOC is considered, the surface bands will only be slightly split. The
application of this theory can be generalized to other unconventional
superconductors with weak SOC, particularly to those with mirror-reflection
symmetry.Comment: 4.5pages, 4 figures plus Appendi
- âŠ