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Register a new userAngular dependence of superconductivity in superconductor / spin valve heterostructures
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We report measurements of the superconducting transition temperature, $T_c$, in CoO/Co/Cu/Co/Nb multilayers as a function of the angle $alpha$ between the magnetic moments of the Co layers. Our measurements reveal that $T_c(alpha)$ is a nonmonotonic function, with a minimum near $alpha={pi}/{2}$. Numerical self-consistent solutions of the Bogoliubov - de Gennes equations quantitatively and accurately describe the behavior of $T_c$ as a function of $alpha$ and layer thicknesses in these superconductor / spin-valve heterostructures. We show that experimental data and theoretical evidence agree in relating $T_c(alpha)$ to enhanced penetration of the triplet component of the condensate into the Co/Cu/Co spin valve in the maximally noncollinear magnetic configuration.
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We have studied the dependence of the superconducting (SC) transition temperature on the mutual orientation of magnetizations of Fe1 and Fe2 layers in the spin valve system CoO_x/Fe1/Cu/Fe2/Pb. We find that this dependence is nonmonotonic when passing from the parallel to the antiparallel case and reveals a distinct minimum near the orthogonal configuration. The analysis of the data in the framework of the SC triplet spin valve theory gives direct evidence for the long-range triplet superconductivity arising due to noncollinearity of the two magnetizations.
In recent years, signatures of Majorana fermions have been demonstrated experimentally in several superconducting systems. However, finding systems which can be scaled up to accommodate a large number of Majorana fermions for quantum computation remains a major challenge for experimentalists. In a recent work [1], signatures of a pair of Majorana zero modes (MZMs) were found in a new experimental platform formed by EuS islands deposited on top of a gold wire which were made superconducting through proximity coupling to a superconductor. In this work, we provide a theoretical explanation for how MZMs can be formed in EuS/Au/superconductor heterostructures. This simple experimental setup provides a new route for realizing a large number of Majorana fermions for quantum computations.
In this communication, we report the temperature dependence (3 to 300K) of the electrical resistivity of BiS2 based layered PrO0.5F0.5BiS2 superconductor at ambient and hydrostatic pressure of up to 3GPa. It is observed that Tc increases with pressure at the rate of dTc/dP=0.45/GPa for PrO0.5F0.5BiS2 compound. It is envisaged that one may increase the Superconducting transition temperature (Tc) of recently discovered PrO0.5F0.5BiS2 superconductor by applying hydrostatic external or internal chemical pressure via suitable on site substitutions.
We have measured the transport properties of Ferromagnet - Superconductor nanostructures, where two superconducting aluminum (Al) electrodes are connected through two ferromagnetic iron (Fe) ellipsoids in parallel. We find that, below the superconducting critical temperature of Al, the resistance depends on the relative alignment of the ferromagnets magnetization. This spin-valve effect is analyzed in terms of spin accumulation in the superconducting electrode submitted to inverse proximity effect.
The theory of superconductor-ferromagnet (S-F) heterostructures with two ferromagnetic layers predicts the generation of a long-range, odd-in-frequency triplet pairing at non-collinear alignment (NCA) of the magnetizations of the F-layers. This triplet pairing has been detected in a Nb/Cu41Ni59/nc-Nb/Co/CoOx spin-valve type proximity effect heterostructure, in which a very thin Nb film between the F-layers serves as a normal conducting (nc) spacer. The resistance of the sample as a function of an external magnetic field shows that for not too high fields the system is superconducting at a collinear alignment of the Cu41Ni59 and Co layer magnetic moments, but switches to the normal conducting state at a NCA configuration. This indicates that the superconducting transition temperature Tc for NCA is lower than the fixed measuring temperature. The existence of a minimum Tc, at the NCA regime below that one for parallel or antiparallel alignments of the F-layer magnetic moments, is consistent with the theoretical prediction of a singlet superconductivity suppression by the long-range triplet pairing generation.
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