FeSe1−x
Te
x
superconductors manifest some intriguing electronic properties depending on the value of x. In FeSe single crystal, the nematic phase and Dirac band structure have been observed, while topological surface superconductivity (SC) with the Majorana bound state was found in the crystal of x∼ 0.55. Therefore, the electronic properties of single crystals with 0 < x ⩽ 0.5 are crucial for probing the evolution of those intriguing properties as well as their relations. However, this study is still left blank due to the lack of single crystals because of phase separation. Here, we report the synthesis, magnetization, electronic transport properties, and hydrostatic pressure effect of FeSe0.67Te0.33 single crystals free of phase separation. A structural (nematic) transition is visible at T
s = 39 K, below which the resistivity exhibits a Fermi-liquid behavior. Analysis of the upper critical fields suggests that spin-paramagnetic effect should be taken into account for both H || c axis and H || ab plane. A crossover from the low-H quadratic to the high-H quasi-linear behavior is observed in the magnetoresistance, signifying the possible existence of Dirac-cone state. Besides, the strong temperature dependence of Hall coefficient, violation of (modified) Kohler’s rule, and two-band model analysis indicate the multiband effects in FeSe0.67Te0.33 single crystals. Hydrostatic pressure measurements reveal that T
s is quickly suppressed with pressure while T
c is monotonically increased up to 2.31 GPa, indicating the competition between nematicity and SC. No signature of magnetic order that has been detected in FeSe1−x
S
x
is observed. Our findings fill up the blank of the knowledge on the basic properties of FeSe1−x
Te
x
system with low-Te concentrations.
Electrical transport of both longitudinal and transverse directions carries rich information. Mobility spectrum analysis (MSA) is capable of extracting charge information from conductivity tensor, including charge types, concentration and mobilities. Using a numerical method based on maximum entropy principle, i.e., maximum entropy mobility spectrum analysis (MEMSA), mobility spectrum for $$\beta $$
β
-type PtBi$$_2$$
2
is studied. Three hole-pockets and two electron-pockets were found, including a small hole pocket with very high mobility, which is very likely corresponding to Dirac Fermions. Benefiting from our high resolution result, we studied temperature dependence of carrier properties and explained the sign change phenomenon of Hall conductivity. We further compared the results with band structure obtained by our first principle calculation. The present results prove MEMSA is a useful tool of extracting carries’ information in recently discovered Iron-based superconductors, and topological materials.
The effects of alkali and alkaline earth metals on the spatial distribution of electron number densities (n,) in an inductively coupled plasma have been studied. An optical fibre probe was used to sample the spatial position of the plasma and the photodiode array spectrometer to detect the HP line. The resultant lateral profiles were subjected to an Abel inversion. An on-line intelligent background correction method was used to correct the background under the HP line, whose full width at half maximum was then calculated automatically. Graphs of three-dimensional spatial distributions of n, in the presence of K, Na and Ca are compared with that of water. At an observation height of 7.2 mm above the load coil, the n, increased with decreasing ionization potentials of the elements. At an observation height of 9.6 mm, no measurable increase of n, is observed except for K.
Conductivity measurements have been made for very dilute solutions of NaCl, KCl, HCl and NaOH. They obey the well-known Onsager's formula quite well at high concentration, but deviate from it at low concentration in the region of about 10 −4 M. The oscillation of conductivity has also been measured for very dilute NaCl solution, where a λ-shape transition is found in the same region. This possibly indicates a phase transition due to the formation of metastable water clusters. * E-mail: Syinlo@ateg.com 885 Mod. Phys. Lett. B 1999.13:885-893. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ DAVIS on 02/08/15. For personal use only.
A gateable, image-intensified laser system that permits detection of latent fingerprints under high background light is described. The system is intended for crime-scene work and for daylight conditions.
An on-line intelligent background correction in ICP-AES using a laboratory-constructed photodiode array (PDA) spectrometer is described. The PDA spectrometer provides a very convenient way for both flexibility in choice of analytical wavelength and fast concurrent acquisition of the data required for on-line background correction. Prior knowledge of sample composition and visual inspection of the spectral window are not required. The method is evaluated by determining Al and La in Ca matrix.
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