Taking into account correlations in a layered two-dimensional（2D）Fermi liquid,aCoulomb-type interaction induces pairing if particle-hole excitations are taken into account.The quasi-particle pairing force is analogo...Taking into account correlations in a layered two-dimensional（2D）Fermi liquid,aCoulomb-type interaction induces pairing if particle-hole excitations are taken into account.The quasi-particle pairing force is analogous to the resonating valence bond（RVB）of elec-trons in a hydrogen or positronium molecule-like structure.It is turned out that scatteringdiagrams from this model allow to evaluate the vertex function Γ.T<sub>c</sub> is hence calculated byusing the pole condition Γ<sup>-1</sup>=0.It has been found out that T<sub>c</sub> can reach quite high values andgives rise to the bell shape,and is related to the particle density,interlayer distance,dielec-tric constant and band mass.PACS numbers:74.65.+n,71.45.Gm.,74.70.Jm.,71.45.Lr.展开更多
In this research, the influence of calcium content on the binding energy and Cooper pairing is investigated for the high temperature superconducting Y1-xCaxBa2Cu3O7-δ compound where x = 0 - 0.2). This is done by usin...In this research, the influence of calcium content on the binding energy and Cooper pairing is investigated for the high temperature superconducting Y1-xCaxBa2Cu3O7-δ compound where x = 0 - 0.2). This is done by using model considering that the formation of Cooper pairs happens during tunneling mechanism of holes between the two CuO2 layers in the YCBCO crystal which are considered as forming adjacent potential wells. In this work, we make some modifications on the mentioned model and a modified equation for the binding energy as a function of Ca concentration is formulated to study the effect of Ca content by considering the change in the distance between the CuO2 layer as a function of Ca. The calculated results agree very well with experimental results. This happens because the Ca2+ substitution for Y3+ leads to decreasing the distance between the two CuO2 layers and hence potential energy of the system will be decreased. This leads to decreasing the binding energy between the Cooper pairs, and decreasing the distance between the two CuO2 layers increasing the tunneling probability of holes between the two CuO2 layers and thus increasing conduction mechanism and thus increasing current density, but this will decrease the energy gap and as a result decrease the critical temperature. The calculated results agree very well with experimental results.展开更多
In this Perspective article we review retrospectively the streamline of our work on iron-based superconductors, and reflect on the mechanism of Cooper pairing in conventional and unconventional, such as iron-based sup...In this Perspective article we review retrospectively the streamline of our work on iron-based superconductors, and reflect on the mechanism of Cooper pairing in conventional and unconventional, such as iron-based superconductors. The main theme of this review is the concept of effective interaction and renormalization group.展开更多
The dynamics of the skew information (SI) is investigated for a single Cooper Pair Box (CPB) interacting with a single cavity field. By suitably choosing the system parameters and precisely controlling the dynamics, n...The dynamics of the skew information (SI) is investigated for a single Cooper Pair Box (CPB) interacting with a single cavity field. By suitably choosing the system parameters and precisely controlling the dynamics, novel connection is found between the SI and entanglement generation. It is shown that SI can be increased and reach its maximum value either by increasing the number of photons inside the cavity or considering the far off-resonant case.The number of oscillations of SI is increased by decreasing this ratio between the Josephson junction capacity and the gate capacity. This leads to significant improvement of the travelling time between the maximum and minimum values.展开更多
This paper examines the quantization of mesoscopic circuit including Josephson junctions. Following Feynman＇s assumption, via the Hamilton dynamic approach and by virtue of the entangled state representation, it cons...This paper examines the quantization of mesoscopic circuit including Josephson junctions. Following Feynman＇s assumption, via the Hamilton dynamic approach and by virtue of the entangled state representation, it constructs Hamiltonian operator for the double-Josephson-junction mesoscopic circuit coupled by a capacitor. Then it uses the Heisenberg equation of motion to derive the induction voltage across each Josephson junction. The result manifestly shows how the voltage is affected by the capacitance coupling.展开更多
A Cooper-pair box biased by a classical voltage and also irradiated by a squeezed state field is considered in order to find new ways to quantum communication and calculation. The quantum dynamics of the Cooper-pair b...A Cooper-pair box biased by a classical voltage and also irradiated by a squeezed state field is considered in order to find new ways to quantum communication and calculation. The quantum dynamics of the Cooper-pair box and the entanglement which is the core theoretics of quantum communication and calculation is investigated in this system, which is related to the squeezing parameter of the squeezed state, A model of Hamiltonian which represents the interaction between box and quantum field is introduced. Finally, the relationship between the entanglement and the squeezing parameter of the squeezed state is demonstrated.展开更多
A Hamiltonian which represents the interaction between a single Cooper-pair box and two quantized electromagnetic fields is considered in order to find new ways for quantum information. The wave function in Schrodinge...A Hamiltonian which represents the interaction between a single Cooper-pair box and two quantized electromagnetic fields is considered in order to find new ways for quantum information. The wave function in Schrodinger picture is obtained. The evolution of the entropy of the box as a function of the scaled time is ploted to measure the entanglement between the box and the fields. It is found that the entanglement is sensitive to the detuning between the Josephson energy and the fields frequency, increasing the detuning can decrease the entanglement.展开更多
Increase of Tc in Al1−x(SiO2)x cermets with increasing x is caused by electron transfer from the Al grains to the SiO2 phase occupying surface states, expressed by Tc/Tc,max=1−γ⋅n2(*), where n is the electron density...Increase of Tc in Al1−x(SiO2)x cermets with increasing x is caused by electron transfer from the Al grains to the SiO2 phase occupying surface states, expressed by Tc/Tc,max=1−γ⋅n2(*), where n is the electron density in the Al phase and γa characteristic parameter. Decrease of Tc in Pb-Cu-sandwiches is attributed to the electron transfer from the Cu film to the Pb film. γand Tc,maxin equation (*) stands for the influence of the electron-phonon interaction and n2for the influence of the electron-electron Coulomb repulsion on Tc. The result that equation (*) holds for both hole-doped cuprate high-temperature superconductivity (HTSC) and Al1−x(SiO2)x cermets is an important indication that common mechanisms underlie HTSC and classical superconductors. The difference between the two is that in HTSC, electron transfer occurs between different electronic bands, but in Al1−x(SiO2)x cermets between different phases.展开更多
基金Supported by Doe through Science Engineering Alliance under the grant No.DE-FG05-94ER25229The numerical calculations were performed on the CRY supercomputer provided by NCSA at UIUC.
文摘Taking into account correlations in a layered two-dimensional（2D）Fermi liquid,aCoulomb-type interaction induces pairing if particle-hole excitations are taken into account.The quasi-particle pairing force is analogous to the resonating valence bond（RVB）of elec-trons in a hydrogen or positronium molecule-like structure.It is turned out that scatteringdiagrams from this model allow to evaluate the vertex function Γ.T<sub>c</sub> is hence calculated byusing the pole condition Γ<sup>-1</sup>=0.It has been found out that T<sub>c</sub> can reach quite high values andgives rise to the bell shape,and is related to the particle density,interlayer distance,dielec-tric constant and band mass.PACS numbers:74.65.+n,71.45.Gm.,74.70.Jm.,71.45.Lr.
文摘In this research, the influence of calcium content on the binding energy and Cooper pairing is investigated for the high temperature superconducting Y1-xCaxBa2Cu3O7-δ compound where x = 0 - 0.2). This is done by using model considering that the formation of Cooper pairs happens during tunneling mechanism of holes between the two CuO2 layers in the YCBCO crystal which are considered as forming adjacent potential wells. In this work, we make some modifications on the mentioned model and a modified equation for the binding energy as a function of Ca concentration is formulated to study the effect of Ca content by considering the change in the distance between the CuO2 layer as a function of Ca. The calculated results agree very well with experimental results. This happens because the Ca2+ substitution for Y3+ leads to decreasing the distance between the two CuO2 layers and hence potential energy of the system will be decreased. This leads to decreasing the binding energy between the Cooper pairs, and decreasing the distance between the two CuO2 layers increasing the tunneling probability of holes between the two CuO2 layers and thus increasing conduction mechanism and thus increasing current density, but this will decrease the energy gap and as a result decrease the critical temperature. The calculated results agree very well with experimental results.
文摘In this Perspective article we review retrospectively the streamline of our work on iron-based superconductors, and reflect on the mechanism of Cooper pairing in conventional and unconventional, such as iron-based superconductors. The main theme of this review is the concept of effective interaction and renormalization group.
文摘The dynamics of the skew information (SI) is investigated for a single Cooper Pair Box (CPB) interacting with a single cavity field. By suitably choosing the system parameters and precisely controlling the dynamics, novel connection is found between the SI and entanglement generation. It is shown that SI can be increased and reach its maximum value either by increasing the number of photons inside the cavity or considering the far off-resonant case.The number of oscillations of SI is increased by decreasing this ratio between the Josephson junction capacity and the gate capacity. This leads to significant improvement of the travelling time between the maximum and minimum values.
基金Project supported by the National Natural Science Foundation of China (Grant No 10574060)the Natural Science Foundation(Grant No Y2004A09) of Shandong Province,China
文摘This paper examines the quantization of mesoscopic circuit including Josephson junctions. Following Feynman＇s assumption, via the Hamilton dynamic approach and by virtue of the entangled state representation, it constructs Hamiltonian operator for the double-Josephson-junction mesoscopic circuit coupled by a capacitor. Then it uses the Heisenberg equation of motion to derive the induction voltage across each Josephson junction. The result manifestly shows how the voltage is affected by the capacitance coupling.
文摘A Cooper-pair box biased by a classical voltage and also irradiated by a squeezed state field is considered in order to find new ways to quantum communication and calculation. The quantum dynamics of the Cooper-pair box and the entanglement which is the core theoretics of quantum communication and calculation is investigated in this system, which is related to the squeezing parameter of the squeezed state, A model of Hamiltonian which represents the interaction between box and quantum field is introduced. Finally, the relationship between the entanglement and the squeezing parameter of the squeezed state is demonstrated.
文摘A Hamiltonian which represents the interaction between a single Cooper-pair box and two quantized electromagnetic fields is considered in order to find new ways for quantum information. The wave function in Schrodinger picture is obtained. The evolution of the entropy of the box as a function of the scaled time is ploted to measure the entanglement between the box and the fields. It is found that the entanglement is sensitive to the detuning between the Josephson energy and the fields frequency, increasing the detuning can decrease the entanglement.
文摘Increase of Tc in Al1−x(SiO2)x cermets with increasing x is caused by electron transfer from the Al grains to the SiO2 phase occupying surface states, expressed by Tc/Tc,max=1−γ⋅n2(*), where n is the electron density in the Al phase and γa characteristic parameter. Decrease of Tc in Pb-Cu-sandwiches is attributed to the electron transfer from the Cu film to the Pb film. γand Tc,maxin equation (*) stands for the influence of the electron-phonon interaction and n2for the influence of the electron-electron Coulomb repulsion on Tc. The result that equation (*) holds for both hole-doped cuprate high-temperature superconductivity (HTSC) and Al1−x(SiO2)x cermets is an important indication that common mechanisms underlie HTSC and classical superconductors. The difference between the two is that in HTSC, electron transfer occurs between different electronic bands, but in Al1−x(SiO2)x cermets between different phases.
