We synthesized (Pb,Cd)Sr2(Y,Ca)Cu2O7+x,phase superconductor.After substitution of Pb with Bi,the BiCd1212 phase shows no superconductivity.Although previous EXAFS study has shown the local structure environment of the...We synthesized (Pb,Cd)Sr2(Y,Ca)Cu2O7+x,phase superconductor.After substitution of Pb with Bi,the BiCd1212 phase shows no superconductivity.Although previous EXAFS study has shown the local structure environment of the Cu is similar in both compounds,EXAFS results of Bi and Pb here demonstrate that σ2 of Pb-Oin-plane is larger than that of Bi-O inplane,whereas σ^2 of Pb-Oapical is smaller than that of Bi-O,wherase σ^2 of Pb-O apical is smaller than that of Bi-Oapical.The Sr shell features are also differnet,it appeared that superconductivity needs some disorder .in carrier reservoir layer,which is due to the substitutional defect caused by different ionic radii.展开更多
On the assumption that a Cooper pair acts as a Bose particle and based on the newly established <η|representation, which is the common eigenvector of two particles' relative position and total momentum, we int...On the assumption that a Cooper pair acts as a Bose particle and based on the newly established <η|representation, which is the common eigenvector of two particles' relative position and total momentum, we introduce a mesoscopic Josephson junction Hamiltonian constituted by two-mode Bose phase operator and number-difference operator. The number-difference-phase uncertainty relation can then be set up, which implies the existence of Josephson current.展开更多
One of the most strikingly universal features of the high-temperature superconductors is that the super- conducting phase emerges in the close proximity of the antiferromagnetic phase, and the interplay between these ...One of the most strikingly universal features of the high-temperature superconductors is that the super- conducting phase emerges in the close proximity of the antiferromagnetic phase, and the interplay between these two phases poses a long-standing challenge. It is commonly believed that, as the antifer- romagnetic transition temperature is continuously suppressed to zero, there appears a quantum critical point, around which the existence of antiferromagnetic fluctuation is responsible for the development of the superconductivity. In contrast to this scenario, we report the observation of a bi-critical point identified at 2,88 GPa and 26.02 K in the pressurized high-quality single crystal Cao.73Lao.27FeAs2 by com- plementary in-situ high pressure measurements. At the critical pressure, we find that the antiferromag- netism suddenly disappears and superconductivity simultaneously emerges at almost the same temperature, and that the external magnetic field suppresses the superconducting transition temperature but hardly affects the antiferromagnetic transition temperature.展开更多
In the last years it has been shown that some properties of strongly coupled superconductors can be potentially described by classical general relativity living in one higher dimension,which is known as holographic su...In the last years it has been shown that some properties of strongly coupled superconductors can be potentially described by classical general relativity living in one higher dimension,which is known as holographic superconductors.This paper gives a quick and introductory overview of some holographic superconductor models with s-wave,p-wave and d-wave orders in the literature from point of view of bottom-up,and summarizes some basic properties of these holographic models in various regimes.The competition and coexistence of these superconductivity orders are also studied in these superconductor models.展开更多
We have synthesized two iron fluo-arsenides ACa2Fe4As4Fz with A = Rb and Cs, analogous to the newly discovered superconductor KCazFe4As4F2. The quinary inor- ganic compounds crystallize in a body-centered tetragonal l...We have synthesized two iron fluo-arsenides ACa2Fe4As4Fz with A = Rb and Cs, analogous to the newly discovered superconductor KCazFe4As4F2. The quinary inor- ganic compounds crystallize in a body-centered tetragonal lattice with space group I4/mmm, which contain double Fe2As2 layers that are separated by insulating Ca2F2 layers. The electrical and magnetic measurements on the polycrys- talline samples demonstrate that the new materials undergo superconducting transitions at Tc = 30.5 and 28.2 K, respec- tively, without extrinsic doping. The correlations between Tc and structural parameters are discussed.展开更多
The spin relaxation time is long in organic semiconductors because of the weak spin-orbit and hyperfine interactions,leading to intensive study on spin transport in organic semiconductors.The rapid progress towards ut...The spin relaxation time is long in organic semiconductors because of the weak spin-orbit and hyperfine interactions,leading to intensive study on spin transport in organic semiconductors.The rapid progress towards utilizing spin degree of freedom in organic electronic devices is occurring.While the spin injection,transport and detection in organic semiconductors are demonstrated,the fundamental physics of these phenomena remains unclear.This paper highlights recent progress that has been made,focusing primarily on present experimental work.展开更多
We elucidate a recently emergent framework in unifying the two families of high temperature （high To） superconductors, cuprates and iron-based superconductors. The unification suggests that the latter is simply the ...We elucidate a recently emergent framework in unifying the two families of high temperature （high To） superconductors, cuprates and iron-based superconductors. The unification suggests that the latter is simply the counterpart of the former to realize robust extended s-wave pairing symmetries in a square lattice. The unification identifies that the key ingredients （gene） of high Tc superconductors is a quasi two dimensional electronic environment in which the d-orbitals of cations that partic- ipate in strong in-plane couplings to the p-orbitals of anions are isolated near Fermi energy. With this gene, the superexchange magnetic interactions mediated by anions could maximize their contributions to superconductivity. Creating the gene requires special arrangements between local electronic structures and crystal lattice structures. The speciality explains why high Tc superconductors are so rare. An explicit prediction is made to realize high Tc superconductivity in Co/Ni-based materials with a quasi two dimensional hexagonal lattice structure formed by trigonal bipyramidal complexes.展开更多
Using classical time-average approximation, critical temperature and condensed solution in holographic pwave superconductors with a time-dependent source is investigated in probe limit. By choosing suitable gauge fiel...Using classical time-average approximation, critical temperature and condensed solution in holographic pwave superconductors with a time-dependent source is investigated in probe limit. By choosing suitable gauge field ansatz, the equation of motion for a vector field is presented. With the help of the Sturm-Liouville equation, concrete values of phase transition temperature and criticaJ frequency are obtained. It is shown that the phase transition temperature enhances as the frequency of the time-dependent source raises in high frequency regime, which means that the operators on the boundary field theory will be easier to condense.展开更多
文摘We synthesized (Pb,Cd)Sr2(Y,Ca)Cu2O7+x,phase superconductor.After substitution of Pb with Bi,the BiCd1212 phase shows no superconductivity.Although previous EXAFS study has shown the local structure environment of the Cu is similar in both compounds,EXAFS results of Bi and Pb here demonstrate that σ2 of Pb-Oin-plane is larger than that of Bi-O inplane,whereas σ^2 of Pb-Oapical is smaller than that of Bi-O,wherase σ^2 of Pb-O apical is smaller than that of Bi-Oapical.The Sr shell features are also differnet,it appeared that superconductivity needs some disorder .in carrier reservoir layer,which is due to the substitutional defect caused by different ionic radii.
文摘On the assumption that a Cooper pair acts as a Bose particle and based on the newly established <η|representation, which is the common eigenvector of two particles' relative position and total momentum, we introduce a mesoscopic Josephson junction Hamiltonian constituted by two-mode Bose phase operator and number-difference operator. The number-difference-phase uncertainty relation can then be set up, which implies the existence of Josephson current.
基金supported by the National Natural Science Foundation of China(91321207,11427805,U1532267,11404384)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(XDB07020300)+2 种基金the National Key Research and Development Program of China(2016YFA0300300)the Russian Foundation for Basic Research(15-02-02040)the U.S.NSF DMREF(DMR-1435672)
文摘One of the most strikingly universal features of the high-temperature superconductors is that the super- conducting phase emerges in the close proximity of the antiferromagnetic phase, and the interplay between these two phases poses a long-standing challenge. It is commonly believed that, as the antifer- romagnetic transition temperature is continuously suppressed to zero, there appears a quantum critical point, around which the existence of antiferromagnetic fluctuation is responsible for the development of the superconductivity. In contrast to this scenario, we report the observation of a bi-critical point identified at 2,88 GPa and 26.02 K in the pressurized high-quality single crystal Cao.73Lao.27FeAs2 by com- plementary in-situ high pressure measurements. At the critical pressure, we find that the antiferromag- netism suddenly disappears and superconductivity simultaneously emerges at almost the same temperature, and that the external magnetic field suppresses the superconducting transition temperature but hardly affects the antiferromagnetic transition temperature.
基金supported by the National Natural Science Foundation of China(Grant Nos.11035008,11375247,11205226 and 11435006)supported by European Union’s Seventh Framework Programme under grant agreements(FP7-REGPOT-2012-2013-1)no 316165+2 种基金the EU-Greece program"Thales"MIS 375734the European Union(European Social Fund,ESF)Greek national funds through the Operational Program"Education and Lifelong Learning"of the National Strategic Reference Framework(NSRF)under"Funding of proposals that have received a positive evaluation in the 3rd and 4th Call of ERC Grant Schemes"
文摘In the last years it has been shown that some properties of strongly coupled superconductors can be potentially described by classical general relativity living in one higher dimension,which is known as holographic superconductors.This paper gives a quick and introductory overview of some holographic superconductor models with s-wave,p-wave and d-wave orders in the literature from point of view of bottom-up,and summarizes some basic properties of these holographic models in various regimes.The competition and coexistence of these superconductivity orders are also studied in these superconductor models.
基金supported by the National Natural Science Foundation of China(90922002 and 11190023)the National Key Research and Development Program of China(2016YFA0300202)
文摘We have synthesized two iron fluo-arsenides ACa2Fe4As4Fz with A = Rb and Cs, analogous to the newly discovered superconductor KCazFe4As4F2. The quinary inor- ganic compounds crystallize in a body-centered tetragonal lattice with space group I4/mmm, which contain double Fe2As2 layers that are separated by insulating Ca2F2 layers. The electrical and magnetic measurements on the polycrys- talline samples demonstrate that the new materials undergo superconducting transitions at Tc = 30.5 and 28.2 K, respec- tively, without extrinsic doping. The correlations between Tc and structural parameters are discussed.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10974084,11222435 and 11023002)the National Basic Research Program of China (Grant Nos. 2010CB923402 and 2013CB922103)+1 种基金the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Fundamental Research Funds for the Central Universities
文摘The spin relaxation time is long in organic semiconductors because of the weak spin-orbit and hyperfine interactions,leading to intensive study on spin transport in organic semiconductors.The rapid progress towards utilizing spin degree of freedom in organic electronic devices is occurring.While the spin injection,transport and detection in organic semiconductors are demonstrated,the fundamental physics of these phenomena remains unclear.This paper highlights recent progress that has been made,focusing primarily on present experimental work.
基金supported by the National Basic Research Program of ChinaNational Natural Science Foundation of Chinathe Strategic Priority Research Program of Chinese Academy of Sciences
文摘We elucidate a recently emergent framework in unifying the two families of high temperature （high To） superconductors, cuprates and iron-based superconductors. The unification suggests that the latter is simply the counterpart of the former to realize robust extended s-wave pairing symmetries in a square lattice. The unification identifies that the key ingredients （gene） of high Tc superconductors is a quasi two dimensional electronic environment in which the d-orbitals of cations that partic- ipate in strong in-plane couplings to the p-orbitals of anions are isolated near Fermi energy. With this gene, the superexchange magnetic interactions mediated by anions could maximize their contributions to superconductivity. Creating the gene requires special arrangements between local electronic structures and crystal lattice structures. The speciality explains why high Tc superconductors are so rare. An explicit prediction is made to realize high Tc superconductivity in Co/Ni-based materials with a quasi two dimensional hexagonal lattice structure formed by trigonal bipyramidal complexes.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 10773002,10875012,and 11175019supported by the Fundamental Research Funds for the Central Universities under Grant No. 105116
文摘Using classical time-average approximation, critical temperature and condensed solution in holographic pwave superconductors with a time-dependent source is investigated in probe limit. By choosing suitable gauge field ansatz, the equation of motion for a vector field is presented. With the help of the Sturm-Liouville equation, concrete values of phase transition temperature and criticaJ frequency are obtained. It is shown that the phase transition temperature enhances as the frequency of the time-dependent source raises in high frequency regime, which means that the operators on the boundary field theory will be easier to condense.
