[en] A series of big single crystals of BaFe_2−xNi_xAs₂ have been prepared by the FeAs self-flux method, with nominal nickel doping x = 0–0.12. The dimensions of the cleaved crystals are over 10 mm along ab plane and ∼2 mm in maximum along the c direction. The measurements of x-ray diffraction, electrical resistance and magnetic property are carried out on the crystals. For the undoped parent compound BaFe₂As₂, both resistance and magnetization data display an anomaly associated with spin density wave and/or structural phase transition, with the transition temperatures at ∼138 K. For Ni-doped BaFe_2−xNi_xAs₂ crystals, the superconducting critical temperature T_c ranges from 4.3 K for x = 0.06 sample to 20 K for the optimally doped x = 0.10 crystal. (condensed matter: structure, thermal and mechanical properties)

[en] Single crystals of undoped and nickel-doped BaFe_2−xNi_xAs₂ (x = 0, 0.04) have been grown by FeAs self-flux method. The maximum dimension of the crystal is as large as ∼ 1 cm along the ab plane. The crystalline topography of a cleaved crystal surface is examined by scanning electron microscope (SEM). By x-ray powder diffraction (XRD) experiments using pure silicon as an internal standard, precise unit cell parameters (tetragonal at room temperature) are determined: a = 3.9606(4) Å (1 Å = 0.1 nm), c = 13.015(2) Å for BaFe_1.96Ni_0.04As₂ and a = 3.9590(5) Å, c = 13.024(1) Å for BaFe₂As₂. DC magnetization and transport measurements are performed to check superconducting transition (T_c = 15 K for x = 0.04) and other subtle anomalies. For BaFe_1.96Ni_0.04As₂ crystal, the resistance curve at normal state shows two distinct anomalies associated with spin and structure transitions, and its magnetization data above ∼ 91 K exhibit a linear temperature dependence due to spin density wave (SDW) instability. (condensed matter: structure, thermal and mechanical properties)

[en] We have grown underdoped (x = 0.11, 0.12) and optimally doped (x = 0.16) La_2–xSr_xCuO₄ single crystals by the traveling-solvent floating-zone technique. In order to prepare good quality cuprate crystals, we have made much effort to optimize the preparation procedures. For example, we haveadopted the sol–gel route to prepare a highly fine and homogeneous La_2–xSr_xCuO₄ precursor powder for fabricating a very dense ceramic feed rod used for the floating-zone growth, and we have also used quite a slow growth rate. The high quality of the grown crystals has been verified by double-crystal x-ray rocking curves, with the full-width-at-half-maximum being only 113–150 arcseconds, which are the best data reported so far for La_2–xSr_xCuO₄ crystals. The superconducting critical temperatures of the grown crystals are 30, 31 and 38.5 K for x = 0.11, 0.12 and 0.16 samples, respectively, according to magnetic measurements. (condensed matter: structure, thermal and mechanical properties)

[en] High quality Pb-doped Bi₂Sr₂CuO_6+δ (Pb-Bi2201) single crystals are grown by the traveling solvent floating zone technique, with dimensions as large as ∼ 50 mm× ∼ 5.0 mm× ∼ 2 mm. The Pb-Bi2201 single crystals with different doping levels are obtained by the annealing process which covers a wide doping range of the overdoped region. We describe in detail the growth and annealing procedures and the characterization and physical property measurements of the Pb-Bi2201 crystals. The availability of these crystals provides a good opportunity to experimentally investigate high-T_c cuprate superconductors, particularly in the overdoped region. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

[en] We report the superconductivity in iron-based oxyarsenide Sm[O_1-xF_x]FeAs, with the onset resistivity transition temperature at 55.0K and Meissner transition at 54.6 K. This compound has the same crystal structure as LaOFeAs with shrunk crystal lattices, and becomes the superconductor with the highest critical temperature among all materials besides copper oxides up to now. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

[en] Preoperative differentiation between benign parotid gland tumors (BPGT) and malignant parotid gland tumors (MPGT) is important for treatment decisions. The purpose of this study was to develop and validate an MRI-based radiomics nomogram for the preoperative differentiation of BPGT from MPGT. A total of 115 patients (80 in training set and 35 in external validation set) with BPGT (n = 60) or MPGT (n = 55) were enrolled. Radiomics features were extracted from T1-weighted and fat-saturated T2-weighted images. A radiomics signature model and a radiomics score (Rad-score) were constructed and calculated. A clinical-factors model was built based on demographics and MRI findings. A radiomics nomogram model combining the Rad-score and independent clinical factors was constructed using multivariate logistic regression analysis. The diagnostic performance of the three models was evaluated and validated using ROC curves on the training and validation datasets. Seventeen features from MR images were used to build the radiomics signature. The radiomics nomogram incorporating the clinical factors and radiomics signature had an AUC value of 0.952 in the training set and 0.938 in the validation set. Decision curve analysis showed that the nomogram outperformed the clinical-factors model in terms of clinical usefulness. The above-described radiomics nomogram performed well for differentiating BPGT from MPGT, and may help in the clinical decision-making process.

[en] We report that a deep ultraviolet (DUV) laser from the sixth harmonic of a 1064 nm laser has been firstly used as light source in an ultrahigh energy-resolution angle-resolved photoemission spectroscopy (ARPES). The wavelength is 177.3nm obtained by using the second harmonic KBe₂BO₃F₂ crystal with a frequency tripled 1064nm Nd:YVO₄ laser. The large flux (10¹⁴ – 10¹⁵ photons/s) and narrow line width (0.26meV) are suitable for the ultrahigh-energy resolution ARPES. The laser-ARPES can be a powerful tool to study the electronic structure at and near the Fermi level of the superconductor and correlated materials. The laser-ARPES has worked more than 500 h already

[en] High resolution angle-resolved photoemission measurements have been carried out to study the superconducting gap in the (Ba_0.6K_0.4)Fe₂As₂ superconductor with T_e = 35 K. Two hole-like Fermi surface sheets around the I' point exhibit different superconducting gaps. The inner Fermi surface sheet shows larger (10 ∼ 12 meV) and slightly momentum-dependent gap while the outer one has smaller (7 ∼ 8meV) and nearly isotropic gap. The lack of gap node in both Fermi surface sheets favours s-wave superconducting gap symmetry. Superconducting gap opening is also observed at the M(π, π) point. The two Fermi surface spots near the M point are gapped below T_e but the gap persists above T_e. The rich and detailed superconducting gap information will provide key insights and constraints in understanding pairing mechanism in the iron-based superconductors

[en] High resolution photoemission measurements are carried out on non-superconducting LaFeAsO parent compound and various superconducting RFeAs(O_1-xF_x) (R=La, Ce and Pr) compounds. It is found that the parent LaFeAsO compound shows a metallic character. By extensive measurements, several common features are identified in the electronic structure of these Fe-based compounds: (1) 0.2 eV feature in the valence band, (2) a universal 13-16 meV feature, (3) near Ef spectral weight suppression with decreasing temperature. These universal features can provide important information about band structure, superconducting gap and pseudogap in these Fe-based materials

[en] High resolution photoemission measurements are carried out on non-superconducting SmOFeAs parent compound and superconducting SmFeAs(O_1-xF_x) (x = 0.12, and 0.15) compounds. The momentum-integrated spectra exhibit a clear Fermi cutoff that shows little leading-edge shift in the superconducting state. A robust feature at 13meV is identified in all these samples. Spectral weight suppression near Ef with decreasing temperature is observed in both undoped and doped samples that points to a possible existence of a pseudogap in these Fe-based compounds