بررسي حالت هاي مقيد آندريو در اتصال جوزفسون ابررسانا-فرومغناطيس-ابررسانا با تقارن موج d

In this thesis, the effect of d-wave magnetism (Altremagnetism) on the spectrum of the an‎dreev levels in a junction between two s-wave superconductors is studied, taking into account the superconducting gap an‎d the phase difference between the two superconducting reservoirs. Compared to a nonmagnetic junction (two s-wave superconductors connected by a nonmagnetic metal), the phase dependence φ of the spectrum is shifted by ±"δ" φ. This shift depends on the spin direction, so that the an‎dreev levels are well spin-polarized. Also in this thesis, in a parallel flat junction with wave symmetry, the excitation energies are determined by the normal mode transition probability T, by the relation "E =" "∆" _"0" √("1-T" 〖"sin" 〗^"2" "(φ±δφ)/2" ) Our framework is the scattering matrix an‎d the Bogoliov-Degenes equation. Here we extend the scattering theory of nonmagnetic Josephson junctions to the case of a altermagnetic junction. The fundamental effect of d-wave magnetization is the spin polarization of the an‎dreev levels by imposing an opposite phase shift (±δϕ) in the energy of the spin-up an‎d spin-down spectra (E(ϕ)). For a planar junction parallel to the crystal axes, the d-wave symmetry is aligned〖 d〗_(x-y) , the phase shift is proportional to the transverse momentum k_y, which is obtained by integrating dE/dϕ over k_y the closed form for the supercurrent. Finally, current-phase diagrams were plotted under different conditions for up an‎d down spins. We obtain that, the current-phase relationship is strongly non-sinusoidal, which is different from the stan‎dard Josephson junction. Our calculations are made under conditions where the junction length L is less than the superconducting coherence length an‎d also less than the mean free path l for impurity scattering.

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