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101.
The heavy fermion system (HFS) is described by the periodic Anderson model (PAM), treating the Coulomb correlation between
the f-electrons in the meanfield Hartree-Fock approximation. Superconductivity is introduced by a BCS-type pairing term among the
conduction electrons. Within this approximation the equation for the superconducting gap is derived, which depends on the
effective position of the energy level of the f-electrons relative to the Fermi level. The latter in turn depends on the occupation probability n
f of the f-electrons. The gap equation is solved self-consistently with the equation for n
f; and their temperature dependences are studied for different positions of the bare f-electron energy level, with respect to the Fermi level. The dependence of the superconducting gap on the hybridization leads
to a re-entrant behaviour with increasing strength. The induced pairing between the f-electrons and the pairing of mixed conduction and f-electrons due to hybridization are also determined. The temperature dependence of the hybridization parameter, which characterizes
the number of electrons with mixed character and represents the number of heavy electrons is studied. This number is shown
to be small. The quasi-particle density of states (DOS) shows the existence of a pseudo-gap due to superconductivity and the
signature of a hybridization gap at the Fermi level. For the choice of the model parameters, the DOS shows that the HFS is
a metal and undergoes a transition to the gap-less superconducting state.
相似文献
102.
Reba Panigrahi Santosh Kumar Sahu Pradyota Kumar Behera Subhalaxmi Panda Prof. Laxmidhar Rout 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(3):620-624
CuII catalyst is less efficient at room temperature for C−S cross-coupling. C−S cross-coupling by CuII catalyst at room temperature is not reported; however, doping of copper with molybdenum metal has been realized here to be more efficient for C−S cross-coupling in comparison to general CuII catalyst. The doped catalyst CuMoO4 nanoparticle is found to be more efficient than copper. The catalyst works under mild conditions without any ligand at room temperature and is recyclable and effective for a wide range of thiols and haloarenes (ArI, ArBr, ArF) from milligram to gram scale. The copper-based bimetallic catalyst is developed and recognized for C−S cross-coupling of haloarenes with alkyl and aryl thiols. 相似文献
103.
Niranjan Panda Ashis Kumar JenaSasmita Mohapatra Smruti Ranjan Rout 《Tetrahedron letters》2011,52(16):1924-1927
The synergistic effects of iron and copper in copper ferrite nanoparticles for the N-arylation of heterocycles with aryl halides were demonstrated. The magnetic nature of the catalyst facilitates its removal from the reaction medium for further use. Negligible leaching of Cu and Fe in consecutive cycles makes the catalyst economical and environmentally benign for C-N cross-coupling reactions. 相似文献
104.
105.
Dibyaranjan Rout Kyoung‐Seok Moon Suk‐Joong L. Kang 《Journal of Raman spectroscopy : JRS》2009,40(6):618-626
This work reports the temperature‐dependent Raman scattering study of mutiferroic BiFeO3 (BFO) bulk ceramics in a wide temperature range of 93–843 K. The polycrystalline samples are sintered at four different temperatures and characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), vibrating sample magnetometry, differential scanning calorimetry (DSC), and optical microscopy. The microstructure shows remarkable changes in terms of grain size and domain pattern as the sintering temperature increases. The DSC curves show prominent exothermic peaks at 645 K, the antiferromagnetic–paramagnetic phase transition temperature. The Raman spectra of all the four specimens reveal strong anomalies in the vicinity of the Neel temperature, which can be attributed to the multiferroic nature of BFO. The Raman scattering studies also reveal considerable spectral changes at a temperature range of 140–200 K in all the specimens, which can be inferred to a further spin–reorientation transition exhibited in BFO at a cryogenic temperature. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
106.
B. Pradhan B.K. Raj G.C. Rout 《Physica C: Superconductivity and its Applications》2009,469(13):721-727
A theoretical model is addressed here to study the interplay of the superconductivity (SC) and the spin density wave (SDW) long range orders in underdoped region in the vicinity of on-set of superconductivity in presence of an external magnetic field. The order parameters are calculated by using Zubarev’s technique of Green’s functions and determined numerically self-consistently. The gap parameters are found to be strongly coupled to each other through their coupling constants. The interplay displays BCS type two gaps in the quasi-particle density of states (DOS) which resemble the tunneling conductance of STM experiments. The gap edges in the DOS appear at ±(z+z1) and ±(z-z1). The applied magnetic field further induces Zeeman splitting which is explained on the basis of spin-filter effect of tunneling experiment. 相似文献
107.
Gilho Kim Jungsik Bang Yunseok Kim S. K. Rout Seong Ihl Woo 《Applied Physics A: Materials Science & Processing》2009,97(4):821-828
Zn1−x
B
x
O (0≤x≤0.04) thin films were deposited by the liquid source misted chemical vapor deposition (LSMCD) method. The thin films were
polycrystalline with grain sizes of 16 nm to 22 nm. The structural, optical, and electrical properties were investigated by
X-ray diffraction, UV-visible spectrophotometry, Raman spectroscopy, and Hall effect measurement. Also scanning electron (SEM)
and atomic force microscopy (AFM) techniques were used in order to determine the morphological and topological characteristics
of the films. The optimal result of Zn1−x
B
x
O films was obtained at x=0.02, with a low resistivity of ≈10−2 Ω cm, and a high transmittancy of 85% in the visible light spectrum (300 nm ∼ 800 nm). 相似文献
108.
We have observed good ferroelectric loops at room temperature in hexagonal HoMnO3 (HMO) bulk ceramics sintered at 1250 °C. Microstructure and ferroelectric hysteresis loops are observed to be dependent on sintering temperature. It is observed that with an increase of sintering temperature, hexagonal a-axis is compressed and c-axis is marginally dilated with overall contraction of the hexagonal unit-cell volume. We explain the origin of ferroelectricity through relative movement of Ho ion and Mn ion within its unit-cell volume, resulting in the distortion of unit-cell volume. We argue that ferroelectric origin of hexagonal HMO at room temperature may be due to the marginal displacement of Ho ion along a-axis, that influences the exchange interaction among the Mn3+ and Ho3+ ions, causing magnetically induced ferroelectricity at room temperature. 相似文献
109.
The results of ab initio calculations of the pressure dependence of Fe magnetism in cubic FeGe are presented. We find that when the pressure-volume scale is set by means of generalized gradient approximation total energies and magnetism is described by means of the local density approximation, the critical pressure at which the magnetic phase transition occurs is estimated at ≈18 GPa, which is in good agreement with experiments. Using the disordered local moment method we find a localized to itinerant model cross-over of Fe magnetism in cubic FeGe, as a function of volume. Moreover, our calculations also suggest subtle signatures of longitudinal spin fluctuations in cubic FeGe, and that the stiffness parameter softens with increasing pressure. We associate the retention of metallicity in FeGe under pressure with the spin-disorder scattering. The effect of spin-orbit coupling on the electronic structure is also discussed. 相似文献
110.