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Diodes are key elements for electronics, optics, and detection. The search for a material combination providing the best performances for the required application is continuously ongoing. Here, we present a superconducting spintronic tunnel diode based on the strong spin filtering and splitting generated by an EuS thin film between a superconducting Al and a normal metal Cu layer. The Cu/EuS/Al tunnel junction achieves a large rectification (up to $\sim40$\%) already for a small voltage bias ($\sim 200$ $\mu$V) thanks to the small energy scale of the system: the Al superconducting gap. With the help of an analytical theoretical model we can link the maximum rectification to the spin polarization of the barrier and describe the quasi-ideal Schottky-diode behavior of the junction. This cryogenic spintronic rectifier is promising for the application in highly-sensitive radiation detection for which two different configurations are evaluated. In addition, the superconducting diode may pave the way for future low-dissipation and fast superconducting electronics., Comment: 17 pages, 12 figures

Resumen del trabajo presentado al 1st Workshop Spain-Taiwan: "2D Materials and Interfaces for Spintronics", celebrado en Barcelona (España) del 23 al 25 de octubre de 2017., Spin-dependent fields acting on superconductivity lead to intriguing phenomena. Under equilibrium conditions these phenomena are attributed to the singlet-triplet conversion of the superconducting condensate. In this talk I first discuss the effect of spin-orbit coupling (SOC) and exchange fields on the properties of hybrid superconducting structures. I distinguish between intrinsic and extrinsic SOC and predict non-dissipative Spin-Hall, Anomalous-Hall, Edelstein and Spin-Galvanic effects in analogy to normal systems with different types of SOC. These predictions open new opportunities for the development of low-dissipation magneto-electronics. In the second part of the talk, I will focus on charge and heat currents in superconducting structures with ferromagnetic insulators (FI). The spin-splitting of the BCS density of the states induced in the superconductor leads to striking phenomena which I will illustrate by briefly discussing few examples: (i) a huge thermoelectric effect in a N-FI-S structure, (ii) the occurrence of a thermophase in S-FI-S structures, (iii) the possibility of using FI-S in high sensitive detectors and thermometers[6], and (iv) a heat valve based on a ferromagnetic Josephson junction.

The investigation of the ultimate limits imposed by quantum mechanics on amplification represents an important topic both on a fundamental level and from the perspective of potential applications. We propose here a novel setup for an optomechanical amplifier, constituted by a mechanical resonator dispersively coupled to an optomechanical cavity asymmetrically driven around both mechanical sidebands. We show that, on general grounds, the present amplifier operates in a novel regime-- which we here call phase-mixing amplification. At the same time, for a suitable choice of parameters, the amplifier proposed here operates as a phase-sensitive amplifier. Furthermore, we show that both configurations allow amplification below the standard quantum limit in a parameter range compatible with current experiments in microwave circuit optomechanics., Comment: 10 pages, 9 figures, typos fixed, figures improved

We describe the far from equilibrium non-local transport in a diffusive superconducting wire with a Zeeman splitting, taking into account the different spin relaxation mechanisms. We demonstrate that due to the Zeeman splitting an injection of a current in a superconducting wire creates a spin accumulation that can only relax via thermalization. In addition the Zeeman splitting also causes a suppression of the spin-orbit and spin-flip scattering rates. These two effects lead to long-range spin and charge accumulations detectable in the non-local signal. Our model explains the main qualitative features of recent experimental results in terms of realistic parameters and predicts a strong dependence of the non-local signal on the orbital depairing effect from an induced magnetic field.