In the hole-doped cuprates, a small number of carriers suppresses antiferromagnetism and induces superconductivity. In the electron-doped cuprates, on the other hand, superconductivity appears only ...in a narrow window of high-doped Ce concentration after reduction annealing, and strong antiferromagnetic correlation persists in the superconducting phase. Recently, Pr(1.3-x)La0.7Ce(x)CuO4 (PLCCO) bulk single crystals annealed by a protect annealing method showed a high critical temperature of around 27 K for small Ce content down to 0.05. Here, by angle-resolved photoemission spectroscopy measurements of PLCCO crystals, we observed a sharp quasi-particle peak on the entire Fermi surface without signature of an antiferromagnetic pseudogap unlike all the previous work, indicating a dramatic reduction of antiferromagnetic correlation length and/or of magnetic moments. The superconducting state was found to extend over a wide electron concentration range. The present results fundamentally challenge the long-standing picture on the electronic structure in the electron-doped regime.
Electro-adhesive gel (EAG) is a functional material that exhibits an electrically controllable adhesive force. The adhesive characteristic of EAG highlights potential applications in fixing or ...handling devices. However, the EAG adhesive area under an applied electric field is often irregular due to particle distribution at the surface, which therefore leads to a large variance in the adhesive force of each sample. This paper proposes the development of an electro-adhesive pillar array (EAPA) to stabilize and improve the performance of the electro-adhesive force regardless of the sample. Electro-hydrodynamic patterning, which is a novel technique to fabricate micro-/nanostructures in a polymer film, is introduced to fabricate the pillar array. The proposed fabrication method and process are first discussed, and a preferred template design is verified. Furthermore, the fabrication process is improved with a UV-curing polymer and surface treatment of the template. The experimental results show that the improved EAPA successfully achieves a higher fixing force with a uniform adhesive area. The proposed EAPA clearly shows a better electro-adhesion performance than conventional EAG.
An energy gap is, in principle, a dominant parameter in superconductivity. However, this view has been challenged for the case of high-Tc cuprates, because anisotropic evolution of a d-wave-like ...superconducting gap with underdoping has been difficult to formulate along with a critical temperature Tc. Here we show that a nodal-gap energy 2ΔN closely follows 8.5 kBTc with underdoping and is also proportional to the product of an antinodal gap energy Δ(*) and a square-root superfluid density √Ps for Bi₂Sr₂CaCu₂O₈+δ, using low-energy synchrotron-radiation angle-resolved photoemission. The quantitative relations imply that the distinction between the nodal and antinodal gaps stems from the separation of the condensation and formation of electron pairs, and that the nodal-gap suppression represents the substantial phase incoherence inherent in a strong-coupling superconducting state. These simple gap-based formulae reasonably describe a crucial part of the unconventional mechanism governing Tc.
Conventional superconductivity is caused by electron-phonon coupling. The discovery of high-temperature superconductors raised the question of whether such strong electron-phonon coupling is realized ...in cuprates. Strong coupling with some collective excitation mode has been indicated by a dispersion "kink". However, there is intensive debate regarding whether the relevant coupling mode is a magnetic resonance mode or an oxygen buckling phonon mode. This ambiguity is a consequence of the energy of the main prominent kink. Here, we show a new landscape of dispersion kinks. We report that heavily overdoping a Bi
Sr
CaCu
O
superconductor results in a decline of the conventional main kink and a rise of another sharp kink, along with substantial energy shifts of both. Notably, the latter kink can be ascribed only to an oxygen-breathing phonon. Hence, the multiple phonon branches provide a consistent account of our data set on the multiple kinks. Our results suggest that strong electron-phonon coupling and its dramatic change should be incorporated into or reconciled with scenarios for the evolution of high-T
superconductivity.
Conventional superconductivity is caused by electron-phonon coupling. The discovery of high-temperature superconductors raised the question of whether such strong electron-phonon coupling is realized ...in cuprates. Strong coupling with some collective excitation mode has been indicated by a dispersion “kink”. However, there is intensive debate regarding whether the relevant coupling mode is a magnetic resonance mode or an oxygen buckling phonon mode. This ambiguity is a consequence of the energy of the main prominent kink. Here, we show a new landscape of dispersion kinks. We report that heavily overdoping a Bi2Sr2CaCu2O8+δ superconductor results in a decline of the conventional main kink and a rise of another sharp kink, along with substantial energy shifts of both. Notably, the latter kink can be ascribed only to an oxygen-breathing phonon. Hence, the multiple phonon branches provide a consistent account of our data set on the multiple kinks. Our results suggest that strong electron-phonon coupling and its dramatic change should be incorporated into or reconciled with scenarios for the evolution of high-Tc superconductivity.
We have carried out hard x-ray photoemission spectroscopy (HAXPES) of Yb1−xZrxB12 (0 x 0.875) to study the effects of electron doping on the Kondo insulator YbB12. The Yb valences of Yb1−xZrxB12 at ...300 K estimated from the Yb 3d HAXPES spectra decreased after substituting Yb with Zr from 2.93 for YbB12 to 2.83 for Yb0.125Zr0.875B12. A temperature dependent valence decrease was found upon cooling for all doping concentrations. We found peak shifts of the B 1s and Zr 3d5/2, and Yb3+ 4f spectra toward the deeper binding-energy with increasing Zr concentration, which indicates a shift of the Fermi level to the higher energy and that of the Yb 4f hole level close to the Fermi level, respectively, due to electron doping. These results qualitatively show the enhanced hybridization between the Yb 4f and conduction-band states with Zr substitution, consistent with magnetic susceptibility measurements.
The estimation of energy expenditure (EE) of grazing animals is of great importance for efficient animal management on pasture. In the present study, a method is proposed to estimate EE in grazing ...animals based on measurements of body acceleration of animals in combination with the conventional Agricultural and Food Research Council (AFRC) energy requirement system. Three-dimensional body acceleration and heart rate were recorded for tested animals under both grazing and housing management. An acceleration index, vectorial dynamic body acceleration (VeDBA), was used to calculate activity allowance (AC) during grazing and then incorporate it into the AFRC system to estimate the EE (EE derived from VeDBA EE) of the grazing animals. The method was applied to 3 farm ruminant species (7 cattle, 6 goats, and 4 sheep). Energy expenditure based on heart rate (EE) was also estimated as a reference. The result showed that larger VeDBA and heart rate values were obtained under grazing management, resulting in greater EE and EE under grazing management than under housing management. There were large differences between the EE estimated from the 2 methods, where EE values were greater than EE (averages of 163.4 and 142.5% for housing and grazing management, respectively); the EE was lower than the EE, whereas the increase in EE under grazing in comparison with housing conditions was larger than that in EE. These differences may have been due to the use of an equation for estimating EE derived under laboratory conditions and due to the presence of the effects of physiological, psychological, and environmental factors in addition to physical activity being included in measurements for the heart rate method. The present method allowed us to separate activity-specific EE (i.e., AC) from overall EE, and, in fact, AC under grazing management were about twice times as large as those under housing management for farm ruminant animals. There is evidence that the conventional energy system can predict fasting metabolism and the AC of housed animals based on accumulated research on energy metabolism and that VeDBA can quantify physical activity separately from other factors in animals on pasture. Therefore, the use of the VeDBA appears to be a precise way to predict activity-specific EE under grazing conditions, and the method incorporating acceleration index data with a conventional energy system can be a simple and useful method for estimation of EE in farm ruminants on pastures.
We report peculiar momentum-dependent anisotropy in the superconducting gap observed by angle-resolved photoemission spectroscopy in BaFe2 (As1-x Px )2 (x = 0.30, Tc = 30 K). Strongly anisotropic gap ...has been found only in the electron Fermi surface while the gap on the entire hole Fermi surfaces are nearly isotropic. These results are inconsistent with horizontal nodes but are consistent with modified s± gap with nodal loops. We have shown that the complicated gap modulation can be theoretically reproduced by considering both spin and orbital fluctuations.
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