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Anisotropic evolution of energy gap in Bi2212 superconductor

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Frontiers of physics 2016年第5期11卷 91-96页

作者： A. P. Durajski Institute of Physics Czestochowa University of Technology Ave. Arrnii Krajowej 19 42-200 Czestochowa Poland

We present a systematic analysis of the energy gap in underdoped Bi2212 superconductor as a function of temperature and hole doping level. Within the framework of the theoretical model containing the electron-phonon and electron-electron-phonon pairing mechanism, we reproduced the measurement results of modern ARPES experiments with very high accuracy. We showed that the energy-gap am- plitude is very weakly dependent on the temperature but clearly dependent on the level of doping. The evidence for a non-zero energy gap above the critical temperature, referred to as a pseudogap, was also obtained.

关键词： high-temperature superconductors anisotropy energy gap Bi2212

energy gap suppression and excess current in TI2Ba2CaCu208 intrinsic Josephson junctions

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Chinese Physics B 2013年第5期22卷 502-504页

作者：王培解伟胡磊刘欣赵新杰何明季鲁张旭阎少林 Department of Electronics Nankai University Tianfin 300071 China

Intrinsic Josephson junctions in misaligned T12Ba2CaCu208 thin film were fabricated on LaA103 substrate. The temperature dependence of the critical current is investigated around liquid nitrogen temperature. In the current voltage characteristic, large voltage jump and lack of resistive branch are observed, which shows good consistency with the intrinsic Josephson junctions. By analyzing the large gap voltage in the curve, great suppression of the energy gap is found. Through discussing the temperature dependence of the gap voltage in liquid nitrogen temperature, it is shown that this phenomenon can be caused by the non-equilibrium quasiparticle injection. The temperature influence on the excess current also confirms the non-equilibrium effect.

关键词： intrinsic Josephson junctions current voltage characteristics energy gap excess current

The energy gap in Breaking Pairs in BCS Theory of Superconductivity

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Progress in Natural Science:Materials International 1993年第6期 504-515页

作者：程开甲 N.W.Institute of Nuclear Technology Beijing 100037 PRC

The present paper is a supplement to Ref.A mathematical presentation is givenin detail to validate the pairing mechanism in BCS theory of superconductivity.BCS theory only dealswith the transitions of pairs with zero total momentum and discards all the remaining terms on the groundthat they are small and insignificant.But this is not always true,especially when transition processes involvethose terms from electrons of broken pairs.It can be shown that the discarded terms in the non-diagonalHamiltonian for the transitions of pairs with non-zero total momentum will be operative in the secularperturbation and contribute additional energy to this“excited mixed state”which is formed by the single elec-trons from the broken pairs and this contribution is enough to compensate for the increase of the energy inbreaking the pairs.Hence it is doubtful whether there really exists energy gap in breaking a pair.Even theground state in the original BCS theory might be fictitious.This statement will be enhanced by anotherproof with all terms of interaction taken into account in the secular perturbation.

关键词： broken pairs pairs with nonzero total momentum energy gap excited mixed state secular perturbation ground state

Single-electron charging and ultrafast dynamics of bimetallic Au_(144−x)Agx(PET)_(60) nanoclusters

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Nano Research 2022年第9期15卷 8573-8578页

作者： Xiangsha Du Hedi Ma Xinwen Zhang Meng Zhou Zhongyu Liu He Wang Gangli Wang Rongchao Jin Department of Chemistry Carnegie Mellon UniversityPittsburghPennsylvania 15213USA Department of Chemistry Georgia State UniversityAtlantaGeorgia 30302USA Department of Physics University of MiamiCoral GablesFlorida 33146USA Department of Chemical Physics University of Science and Technology of ChinaHefei 230026China

Alloying is an important strategy in tailoring the functionality of materials.In metal nanoclusters(NCs),the introduction of a heterometal leads to alloy nanoclusters that often outperform the homometal ones in terms of the physical and chemical properties.In this work,a series of four M_(144)(PET)60 alloy NCs(where,M=Au/Ag,PET=–SCH_(2)CH_(2)Ph)are synthesized and characterized.The silver doping into the homogold template(Au_(144))leads to more prominent optical absorption features in the steady-state spectrum in the visible range.Femtosecond transient absorption spectroscopy reveals the effect of Ag doping on the electronic relaxation dynamics compared to Au_(144)and the pump fluence independent dynamics.Electrochemical results reflect a narrowing of HOMO–LUMO gap(E_(g))induced by Ag doping.A temperature dependence of the single-electron charging is also observed for the series of alloy NCs,in which the E_(g)values of the alloy NCs enlarge as the temperature decreases,which is characteristic of semiconducting behavior.

关键词： 144-atom alloy nanoclusters Ag doping single-electron charging electron dynamics energy gap

Crystal Sizes and energy gaps of Cerium Oxide Using Co-Precipitation Method

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Materials Sciences and Applications 2022年第4期13卷 213-231页

作者： Paochi Chen Lunghwa University of Science and Technology Taiwan

Co-precipitation was used to prepare cerium oxide nano-particles. The effects of aging temperature and concentration of cobalt ion on the optical property, morphology, and particle size were investigated. The cerium oxide was prepared by adding ammonia solution into a mixed solution of cerium nitrate with cobalt nitrate solutions to obtain a large amount of precipitates and then aged further. Subsequently, the precipitates were kept in an oven for calcination keeping the temperature at 400?C for lasting 24 h. The average size of cerium oxide particles was obtained from the (111) peak in the X-ray diffraction pattern using the Scherrer equation. The crystal sizes obtained were found to be in the range of 11.82 - 13.47 nm. The results showed that the particle size decreased with an increase in the Co ion concentration and decreased with an increase in temperature. The SEM pictures show that the morphology for cerium oxide is granular and/or columnar. It can be seen from UV/Vis absorption spectrum that the maximum absorption peaks were in the range of 334 - 390 nm, depending on the operating conditions. The corresponding energy gaps were observed in the range of 3.18 - 3.71 eV. Subsequently, the Brus equation for the energy gap was discussed. Finally, particle size was correlated with the aging temperature and Co ion concentration.

关键词： Co-Precipitation Hydrothermal Method Cerium Oxide energy gap

energy spectrum of fermionized bosonic atoms in optical lattices

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Chinese Optics Letters 2005年第11期3卷 621-624页

作者：韩玖荣张海潮王育竹 Department of Physics Yangzhou University Yangzhou 225002 Laboratory for Quantum Optics Shanghai Institute of Optics and Fine Mechanics Center for Cold Atom Physics Chinese Academy of Sciences Shanghai 201800 Laboratory for Quantum Optics Shanghai Institute of Optics and Fine Mechanics Center for Cold Atom Physics Chinese Academy of Sciences Shanghai 201800 Laboratory for Quantum Optics Shanghai Institute of Optics and Fine Mechanics Center for Cold Atom Physics Chinese Academy of Sciences Shanghai 201800

We investigate the energy spectrum of fermionized bosonic atoms, which behave very much like spinless noninteracting fermions, in optical lattices by means of the perturbation expansion and the retarded Green＇s function method. The results show that the energy spectrum splits into two energy bands with single-occupation; the fermionized bosonic atom occupies nonvanishing energy state and left hole has a vanishing energy at any given momentum, and the system is in Mott-insulating state with a energy gap. Using the characteristic of energy spectra we obtained a criterion with which one can judge whether the Tonks-Girardeau （TG） gas is achieved or not.

关键词： Atoms Electron energy levels energy gap Expansion Green's function Spectrum analysis

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Silver content effects on energy gap and crystal texture of Ag-TiO2 thin films prepared by RF magnetron sputtering

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Silver content effects on energy gap and crystal texture of ...

First-principles study of structures and electronic properties of cadmium sulfide clusters

TFC’09全国薄膜技术学术研讨会

作者：孟凡明鲁飞 School of Physics and Materials Science Anhui University State Key Laboratory of Materials Modification by Laser Ion and Electron BeamsDalian University of Technology Anhui Key Laboratory of Information Materials and Devices Anhui University

Ag-TiO nanostructured thin films were deposited on silicon and quartz substrates by RF magnetron sputtering.The crystal texture and optical properties of the films were characterized by X-ray diffractometer and ultrav... 详细信息

关键词： Silver TiO2 thin films Crystal texture energy gap RF magnetron sputtering

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Chinese Physics B 2008年第7期17卷 2478-2483页

作者：楚合营刘朝霞邱国莉孔德国武四新李蕴才杜祖亮 Key Laboratory of Special Functional Materials Henan University

The lowest-energy structures and the electronic properties of CdnSn （n = 1 - 8） clusters have been studied by using denslty-functional theory simulating package DMol^3 in the generalized gradient approximation （GGA）. The ring-like structures are the lowest-energy configurations for n = 2, 3 and the three-dimensional spheroid configurations for n = 4 - 8. The three-dimensional structures may be considered as being built from the Cd2S2 and Cd3S3 rings. Compared to the previous reports, we have found the more stable structures for CdnSn（n = 7, 8）. Calculations show that the magic numbers of CdnSn （n = 1-8） clusters are n = 3 and 6. As cluster size increases, the properties of CdnSn clusters tend to bulk-like ones in binding energy per CdS unit and Mulliken atomic charge, obtained by comparing with the calculated results of the wurtzite and zinc blende CdS for the same simulating parameters.

关键词： GGA DMol^3 energy gap binding energy

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Electronic Structure and Optical Properties of La-Doped SrTiO3 and Sr2TiO4 by Density Function Theory

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Chinese Physics Letters 2009年第1期26卷 264-267页

作者：贠江妮张志勇闫军锋赵武 School of Information Science and Technology Northwest University Xi'an 710127

The effect of La doping on the electronic structure and optical properties of SrTiO3 and Sr2 TiO4 is investigated by the first-principles calculation of plane wave ultrasoft pseudopotential based on the density function theory （DFT）. The calculated results reveal that the electron doping in the case of Sr0.875La0.125 TiO3 and Sr1.875Lao.125TiO4 can be described within the rigid band model. The La^3＋ ions fully acts as electron donors in Sr0.875La0.125 TiO3 and Sr1.875 La0.125 TiO4 systems and the Fermi level shifts further into the conduction bands （CBs） for Sr1.875Lao.125 TiO4 compared to Sr0.875 Lao. 125 TiO3. The two systems exhibit n-type degenerate semiconductor features. At the same time, the density of states （DOS） of the two systems shift towards low energies and the optical band gaps are broadened. The Sr1.875La0.125 TiO4 is highly transparent with the transmittance about 90% in the visible range, which is larger than that of Sr0.875Lao.125 TiO3（85%）. The wide band gap, small transition probability and weak absorption due to the low partial density of states （PDOS） of impurity in the Fermi level result in the optical transparency of the films.

关键词： conduction bands density functional theory electronic density of states energy gap Fermi level