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Injection Efficiency of Spin-Polarized quasi-particles in Y-Ba-Cu-O Thin Film

Chinese Physics Letters 2003年第10期20卷 1848-1851页

作者：杨名曹春海张世远杨森祖崔旭高尤立星吉争鸣康琳许伟伟 InstituteofSuperconductorElectronics DepartmentofElectronicScienceandEngineeringNanjingUniversityNanjing210093 DepartmentofPhysics NanjingUniversityNanjing210093

The injection efficiency of spin-polarized quasi-particles in a superconducting Y-Ba-Cu-O (YBCO) film is investigated by means of current injection into the Nd0.7Sr0.3MnO3/SrTiO3/YBa2Cu3O7-δ heterostructures. We have successfully prepared six injection junction windows in the YBCO thin film strip, which are all 56 μm wide, but 80 μm, 40 μm, 20 μm, 10 μm, 5 μm, and 2 μm long, respectively. At 16 K, our YBCO thin film strip (80 nm thick) has Jc = 2×105A/cm2. Under the spin-polarized injection current of Iinj = 0.5 mA, with decreasing injection junction length L, injection efficiency η (η≡ΔJc/ΔJinj; ΔJc: the suppression of critical current density due to finite ΔJinj) increases gradually, until L is not more than 20 μm. In that case, η hardly varies with the change of L, reaching up to about 6. We think that these results are related to the spin diffusion length of spin-polarized quasi-particles in the superconducting thin film. In our heterostructures, the YBCO thin film keeps good superconductivity and the injection junction windows are of proper size, therefore, we have obtained relatively high injection efficiency of spin-polarized quasi-particles.

关键词： Superconducting thin films diffusion length Injections Film strips input current thin films quasi-particles Yttrium barium copper oxides current injection

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The Gravitational Radiation Emitted by Two quasi-particles around a Schwarzschild Black Hole

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Journal of Modern Physics 2018年第6期9卷 1195-1214页

作者： Amos S. Kubeka Department of Mathematical Sciences University of South Africa Pretoria South Africa

We model analytically a relativistic problem consisting of two quasi-particles each with mass m in close orbit around a static Schwarzschild black hole with mass M = 1 situated at the center of mass of the system. The angular momentum l of the system is taken to be 2. We model the mass density of the orbiting particles as a δ-function and we assume that there are no deformations. To model the system, we apply the second-order differential equation obtained elsewhere for a dynamic thin matter shell on a Schwarzschild background. As it is the case in this paper, the framework on which the equation was obtained is Bodi-Sachs. The only change in the equation is that now the quasi-normal mode parameter represents the particle’s orbital frequency from which we are able to analytically compute the gravitational radiation emitted by the system at null infinity. We note that in a real astrophysical scenario the dynamics of the particles paths will be very dynamic and complicated and that the analytical methods used here will have to be developed further to accommodate that.

关键词： Gravitational Radiation Schwarzschild Black Hole quasi-particles quasi-Normal Mode Null Formalism

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