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1.
The superconductivity mechanism of Pb thin film on a Si substrate in the weak interaction regime is investigated. A discrete Fermi surface is constructed depend on the film thickness and electron density and crystallographic orientation. We consider two types of Cooper pair interactions, Cooper pair interaction at thin film surfaces and Cooper pair in the thin film volume. We have chosen the surface Cooper pair interaction, of ultra thin films superconductor proportional to the inverse of thin film thickness, while the volume Cooper pair interaction has been considered as a constant. By these assumptions, we have found oscillation feature of critical temperature Tc and energy gap Δ in terms of thin film thickness similar to the experimental results for Pb/Si(111) thin film superconductor. However, by increasing number of Pb layers, the thin film Tc goes to bulk Tc. In contrast to the previous claimed constant value for the Δb(T=0)/kBTc in bulk, we have found oscillation of this parameter in terms of thin film thickness similar to the Tc oscillation. 相似文献
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3.
LetR be a matrix unitary quasi-classical solution of the Yang-Baxter equation. Considering an associative algebra defined by the
relationRT
1
T
2=T
2
T
1 we find a universal twistF such thatR is the image ofR=F
21
F
−1 in the vector representation.
Presented at the 11th Colloquium “Quantum Groups and Integrable Systems”, Prague, 20–22 June 2002. 相似文献
4.
G.E. Akpojotor 《Physics letters. A》2008,372(46):6992-6995
The issue of how superconductivity originate in the CuO2 planes believed to be crucial to understanding the high Tc superconducting cuprates is still an going debate. In the wake of recent experimental observations of the Zhang-Rice singlet (ZRS), its formation and propagation need to be revisited especially by using a simple approach almost at a phenomenological level. Within a highly simplified correlated variational approach (HSCVA) in this Letter, a new formation of the ZRS as constituting the ground state of a single-band t-J model of the CuO2 planes is developed. This formation is then used to demonstrate how the ZRS can be propagated as a probable Cooper channel in the CuO2 planes. 相似文献
5.
G.E. Moore M.E. Cobern H.T. Fortune S. Mordechai R.V. Kollarits R. Middleton 《Physics letters. [Part B]》1978,76(2):192-194
States populated in the 15N(t,p)17N reaction at 15 MeV are compared with those in the 16O(t,p)18O reaction at the same energy. On the basis of this comparison several spins and parities are assigned. Cross-section ratios are in rough agreement with a weak-coupling model. 相似文献
6.
F. Pegoraro 《Physics letters. A》2008,372(19):3456-3460
A simple algebraic model is constructed with the aim of investigating the time evolution of the symmetry properties of a nonlinear continuous system. The model is constructed so as to mimic the dynamics of a two-dimensional inviscid flow bounded by periodic conditions, but can easily generalized to more complex dynamics involving magnetized plasma configurations. 相似文献
7.
Experimentally observed optical absorption spectra of isolated pairs of chromium ions in Cs3Cr2Br9 corresponding to transitions of pairs from the ground (4 A 2×2 A 2) state to a singly excited (4 A 2×2 T 2) state are theoretically interpreted. It is shown that the position of the exchange multiplets in the excited (4 A 2×2 T 2) state is determined mainly by the resonance exchange interactions removing the degeneracy with respect to the exchange by an excitation within the pair. It is established that the observed fine structure of the pair in the (4 A 2×2 T 2) state is due to a superposition of the contributions from the one-and two-center spin-orbit interaction and resonance antisymmetric exchange. 相似文献
8.
9.
F. Barranco P.F. Bortignon R.A. Broglia G. Colò E. Vigezzi 《The European Physical Journal A - Hadrons and Nuclei》2001,11(4):385-392
If neutrons are progressively added to a normal nucleus, the Pauli principle forces them into states of higher momentum. When
the core becomes neutron saturated, the nucleus expels most of the wave function of the last neutrons outside to form a halo,
which, because of its large size, can have a lower momentum. It is an open question how nature stabilizes such a fragile system
and provides the glue needed to bind the halo neutrons to the core. Here, we show that this problem is similar to that of
the instability of the normal state of an electron system at zero temperature solved by Cooper, a solution which is at the
basis of BCS theory of superconductivity. By mimicking this approach using, aside from the bare nucleon-nucleon interaction,
the long wavelength vibrations of the nucleus 11Li, the paradigm of halo nuclei, as tailored glues of the least bound neutrons, we are able to obtain a unified and quantitative
picture of the observed properties of 11Li.
Received: 9 May 2001 / Accepted: 17 November 2001 相似文献
10.
New generation of Cooper pair splitters defined on hybrid nanostructures are devices with high tunable coupling parameters. Transport measurements through these devices revealed clear signatures of interference effects and motivated us to introduce a new model, called the 3-sites model. These devices provide an ideal playground to tune the Cooper pair splitting (CPS) efficiency on demand, and displays a rich variety of physical phenomena. In the present work we analyze theoretically the conductance of the 3-sites model in the linear and non-linear regimes and characterize the most representative features that arise by the interplay of the different model parameters. In the linear regime we find that the local processes typically exhibit Fano-shape resonances, while the CPS contribution exhibits Lorentzian-shapes. Remarkably, we find that under certain conditions, the transport is blocked by the presence of a dark state. In the non-linear regime we established a hierarchy of the model parameters to obtain the conditions for optimal efficiency. 相似文献
11.
A. G. Prudius 《Russian Physics Journal》1972,15(1):18-22
This paper considers the problem of quantization of electron energy in the presence of joining bands in group D
2h
16
semiconductors. The electron's energy is calculated using continued fractions. It is shown that one can calculate the electron's energy with any degree of accuracy.Translated from Izvestiya VUZ. Fizika, Vol. 15, No. 1, pp. 28–33, January, 1972. 相似文献
12.
Dr. Albert Schmid 《Zeitschrift für Physik B Condensed Matter》1968,8(2):129-140
Electron-phonon and electron-electron collisions are the processes which determine the relaxation timeτ R of the Cooper pair density. The case is considered for which the deviation of the pair density from equilibrium is small and where the equilibrium state is homogeneous. Starting from the Eliashberg equation, one is able to reduce the problem to a quadrature once the equilibrium Green functions are known. If the deviation is constant in space, andT/T c?0.5, we find \(\tau _R \approx \sqrt {T_c /(T_c - T)} \tau _c\) , whereτ c is the collision time (≈10?8 sec). For a deviation modulated in space,τ R very quickly reaches the limiting valueτ c. 相似文献
13.
Cr3+ centers with monoclinic symmetry in SrF2:Cr crystals are studied by EPR. Based on an analysis of the EPR data and a study of the conditions under which the observed
samples were formed, a model is proposed which explains the low symmetry of the magnetic properties in terms of the simultaneous
effect on the impurity ion state of interactions with the interstitial F− ion and with normal vibrations of the crystal lattice in a trigonal symmetry.
Fiz. Tverd. Tela (St. Petersburg) 39, 302–305 (February 1997) 相似文献
14.
We propose a route to a one-dimensional Fulde-Ferrell-Larkin-Ovchinnikov state in the absence of broken time-reversal symmetry.
At present such a state may be encouraged in a clean (no disorder) AlAs quantum wire fabricated using the cleaved edge overgrowth
technique. The fabrication technique captures two degenerate nonoverlapping bands separated in momentum-space by half an umklapp
vector which leads to four Fermi points. Using field theoretic methods such as abelian bosonization and the renormalization
group scheme we treat the important low energy long wavelength fermionic interaction terms for this one dimensional system.
Due to the specific bandstructure arrangement of the quantum wire there is a new class of unique umklapp assisted interactions.
These umklapp interactions are present at all electronic densities and are not related to the commensurability of the electron
gas with the underlying lattice. We show that in the presence of the umklapp interactions and without any external perturbations
such as a magnetic or electric field a singlet superconducting ground state is preferred with non-zero center-of-mass momentum
for the Cooper pairs. The finite pairing momentum of the Cooper pairs is an indication of a Fulde-Ferrell-Larkin-Ovchinnikov
state which is known to lead to inhomogeneous superconductivity. 相似文献
15.
J. Kapusta 《Physics letters. [Part B]》1984,136(3):201-203
Chiral symmetry in the high-temperature plasma phase of QCD is consistent with at least three qualitatively different quark dispersion relations. The rate for , with zero total momentum of the e+e? pair in the plasma rest frame is direct measure of the quark dispersion relation. For the three plausible dispersion relations the rates differ by orders of magnitude when the e+e? invariant mass M < 2T. 相似文献
16.
A new set of trial functions for 1s^22sns configurations in a beryllium atom is suggested. A Mathematica program based on the variational method is developed to calculate the wavefunctions and energies of 1s^22sns (n = 3 - 6) configurations in a beryllium atom. Non-relativistic energy, polarization correction and relativistic correction which include mass correction, one- and two-body Darwin corrections, spin-spin contact interaction and orbit-orbit interaction, are calculated respectively. The results are in good agreement with experimental data. 相似文献
17.
18.
Quantum communication via controlled holes in the statistical distribution of excitations in a nanoresonator coupled to a Cooper pair box
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We propose a scheme to transmit information via the statistical distribution of excitations of a nanomechanical resonator. It employs a controllable coupling between this system and a Cooper pair box. The success probability and the fidelity are calculated and compared with those obtained in an atom-field system in different regimes. Addtionaly, the scheme can also be applied to prepare low excited Fock states. 相似文献
19.
Quantum communication via controlled holes in the statistical distribution of excitations in a nanoresonator coupled to a Cooper pair box
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We propose a scheme to transmit information via the statistical distribution of excitations of a nanomechanical resonator.It employs a controllable coupling between this system and a Cooper pair box.The success probability and the fidelity are calculated and compared with those obtained in an atom-field system in different regimes.Addtionaly,the scheme can also be applied to prepare low excited Fock states. 相似文献
20.
依据量子理论与配位场理论,利用群论和对称性分析的方法探讨了C42+分子在具有D4h对称性构型时,E(b1g+b2g)系统的Jahn-Teller效应中的相关问题.研究了C42+分子的电子态与声子态的对称性及其活跃声子态,讨论了系统声子间的耦合与CG系数,构建了E(b1g+b2g)系统的电声耦合哈密顿量,利用幺正平移变换将系统变换到了无声子激发的空间中,由此计算出了系统无声子激发的基态与激发态及其能级,结果表明由于系统的电声耦合作用缘故,在系统的势能面上形成了四个对称性势阱.无论系统处在哪一个势阱中,在Jahn-Teller畸变之后,系统的二重简并的能级都将发生分裂,分裂后系统电子态的简并性完全被消除.文中利用群论又进一步探讨了系统的Jahn-Teller畸变方向及其基态对称性,发现系统将沿着D4h→D2h方向发生畸变.畸变后C24+分子的基态具有D2h群下的B1u对称性. 相似文献