[en] Gamma-ray relative intensities determined with a HPGe spectrometer must be corrected for cascade coincidence when a soruce with cascade transition is placed close to the detector surface. Generally, normal correction method is approximate calculation from simplified decay scheme, thus the method is suitable for simple decay scheme or case of small cascade correction. The present research promoted a complicated correction method, and a computer program was developed to calculate the cascade correction in a complex spectrum. In order to test the reliability of program, a standard source of ¹⁵²Eu was measured and the test results show that this method can be applied to the cascade correction for complex decay scheme. (authors)

[en] The cumulative fission yields of short-lived nuclides ⁸⁸Rb, ⁹⁵Y, ¹⁰¹Mo, ¹⁰¹Tc, ¹³⁸Cs^g, and ¹⁴²La in thermal neutron induced fission of ²³⁹Pu have been determined by gamma-ray spectrometry relative method. ⁹⁷Zr is selected as the reference nuclide. The determined cumulative fission yields are given as following: the Y(⁸⁸Rb) = (1.32 ± 0.05)%, Y(⁹⁵Y) = (4.69 ± 0.22)%, Y(¹⁰¹Mo) = (6.13 ± 0.32)%, Y(¹⁰¹Tc) = (6.10 ± 0.22)%, Y(¹³⁸Cs^g) = (6.24 ± 0.24)%, Y(¹⁴²La) = (4.74 ± 0.17)%. The major work include HPGe detector efficiency calibration, sample sealing and irradiation, gamma-ray measurement and data analysis. The determined nuclides are located in left, middle, right of light group ,and in middle, right of heavy group for asymmetric fission model. The accurate yields data supply a gap for domestic nuclear database, and reflect the fission products mass distribution character in thermal neutron induced fission of ²³⁹Pu. (authors)

[en] The relative cumulative yields of 62 fission products were determined using γ-spectrum method for ²³²Th induced by 14.8 MeV neutron. Using chain yields summation 200% normalization method, 47 chain yields were given, and the data precision is better than 10%. (authors)

[en] 35 chain yields are determined for the fission of ²³⁵U induced by 19.1 MeV neutrons by HPGe γ-ray spectrometry. Absolute fission rate is monitored with a double-fission chamber. The efficiency of the fission chamber is checked with absolute determination of ¹⁹⁸Au activity from ¹⁹⁷Au (n, γ)¹⁹⁸Au reaction for the first time. Fission product activities of irradiated ²³⁵U foils are measured by HPGe γ-ray spectrometry without chemical separation. Threshold detector method is used to estimate the fission events induced by neutrons of other energies

[en] The recent discovery of superconductivity in the twisted bilayer graphene has stimulated numerous theoretical proposals concerning its exact gap symmetry. Among them, the d+ id or p+ ip-wave was believed to be the most plausible solution. Here, considering that the superconductivity emerges near a correlated insulating state and may be induced by antiferromagnetic spin fluctuations, we apply the strong-coupling Eliashberg theory with both inter- and intraband quantum critical pairing interactions and discuss the possible gap symmetry in an effective low-energy four-orbital model. Our calculations reveal a nodeless s^±-wave as the most probable candidate for the superconducting gap symmetry in the experimentally relevant parameter range. This solution is distinctly different from previous theoretical proposals. It highlights the multi-gap nature of the superconductivity and puts the twisted bilayer graphene in the same class as the iron-pnictide, electron-doped cuprate, and some heavy fermion superconductors. (rapid communication)

[en] Chain yields of 32 chains were determined for the fission of ²³⁸U induced by 22.0 MeV mono-energetic neutrons for the first time. Fission product activities were measured by HPGe γ ray spectrometry without chemical separation. Absolute fission rate was monitored with a double fission chamber. The efficiency of the fission chamber was checked by determination of ¹⁹⁸Au activity from ¹⁹⁷Au(n, γ)¹⁹⁸Au reaction

[en] The two-fluid model is a phenomenological description of the gradual change of the itinerant and local characters of f-electrons with temperature and other tuning parameters and has been quite successful in explaining many unusual and puzzling experimental observations in heavy electron materials. We review some of these results and discuss possible implications of the two-fluid model in understanding the microscopic origin of heavy electron physics. (report on progress)

[en] Nematic order and its fluctuations have been widely found in iron-based superconductors. Above the nematic order transition temperature, the resistivity shows a linear relationship with the uniaxial pressure or strain along the nematic direction and the normalized slope is thought to be associated with nematic susceptibility. Here we systematically studied the uniaxial pressure dependence of the resistivity in Sr_1−xBa_xFe_1.97Ni_0.03As₂, where nonlinear behaviors are observed near the nematic transition temperature. We show that it can be well explained by the Landau theory for the second-order phase transitions considering that the external field is not zero. The effect of the coupling between the isotropic and nematic channels is shown to be negligible. Moreover, our results suggest that the nature of the magnetic and nematic transitions in Sr_{1 − x}Ba_xFe₂As₂ is determined by the strength of the magnetic-elastic coupling. (paper)

[en] Kondo semimetal CeRu₄Sn₆ is attracting renewed attention due to the theoretically predicted nontrivial topology in its electronic band structure. We report hydrostatic and chemical pressure effects on the transport properties of single- and poly-crystalline samples. The electrical resistivity ρ(T) is gradually enhanced by applying pressure over a wide temperature range from room temperature down to 25 mK. Two thermal activation gaps estimated from high- and low-temperature windows are found to increase with pressure. A flat ρ(T) observed at the lowest temperatures below 300 mK appears to be robust against both pressure and field. This feature as well as the increase of the energy gaps calls for more intensive investigations with respect to electron correlations and band topology. (paper)

[en] Understanding the emergence and subsequent behavior of heavy electrons in Kondo lattice materials is one of the grand challenges in condensed matter physics. From this perspective we review the progress that has been made during the past decade and suggest some directions for future research. Our focus will be on developing a new microscopic framework that incorporates the basic concepts that emerge from a phenomenological description of the key experimental findings. (report on progress)