The emerging field of superconductor (SC) spintronics has attracted intensive attentions recently.Many fantastic spin dependent properties in SCs have been discovered, including large magnetoresistance, long spin lifetimes and the giant spin Hall effect, etc. Regarding the spin dynamics in superconducting thin films, few studies has been reported yet. Here, we report the investigation of the spin dynamics in a s-wave superconducting NbN film via spin pumping from an adjacent insulating ferromagnet GdN film. A profound coherence peak of the Gilbert damping of GdN is observed slightly below the superconducting critical temperature of the NbN, which agrees well with recent theoretical prediction for s-wave SCs in the presence of impurity spin-orbit scattering. This observation is also a manifestation of the dynamic spin injection into superconducting NbN thin film. Our results demonstrate that spin pumping could be used to probe the dynamic spin susceptibility of superconducting thin films, thus pave the way for future investigation of spin dynamics of interfacial and two dimensional crystalline SCs.

Spin-orbit coupling (SOC) is a key interaction in spintronics, allowing an electrical control of spin or magnetization and, vice versa, a magnetic control of electrical current. However, recent advances have revealed much broader implications of SOC that is also central to the design of topological states, including topological insulators, skyrmions, and Majorana fermions, or to overcome the exclusion of two-dimensional ferro-magnetism expected from the Mermin-Wagner theorem. SOC and the resulting emergent interfacial spin-orbit fields are simply realized in junctions through structural inversion asymmetry, while the anisotropy in magnetoresistance (MR) allows for their experimental detection. Surprisingly, we demonstrate that an all-epitaxial ferromagnet/ MgO/metal junction with only a negligible MR anisotropy undergoes a remarkable transformation below the superconducting transition temperature of the metal. The superconducting junction has a three orders of magnitude higher MR anisotropy and supports the formation of spin-triplet superconductivity, crucial for superconducting spintronics, and topologically-protected quantum computing. Our findings call for revisiting the role of SOC in other systems which, even when it seems negligible in the normal state, could have a profound influence on the superconducting response.For over 150 years magnetoresistive effects have provided attractive platforms to study spin-dependent phenomena and enable key spintronic applications [1]. Primarily, spintronics relies on junctions with at least two ferromagnetic layers to provide sufficiently large magnetoresistance (MR). Record room-temperature MR and commercial applications employ junctions of common ferromagnets, such as Co and Fe with MgO tunnel barrier [2,3]. Alternatively, MR occurs in single ferromagnetic layers with an interplay of interfacial spin-orbit coupling (SOC). However, in metallic systems this phenomenon, known as the tunneling anisotropic MR (TAMR) [4], is typically < 1% and precludes practical applications. Here we show experimentally that a negligible MR in an all-epitaxial ferromagnet/MgO/metal junction is drastically enhanced below the superconducting transition temperature of the metal. We explain this peculiar behavior with the role of the interfacial SOC in the formation of spin-triplet superconductivity which can enable low-power superconducting spintronics [5-7] and topologically-protected quantum computing [8,9].

Wearable devices have found widespread applications in recent years as both medical devices as well as consumer electronics for sports and health tracking. A metric of health that is often overlooked in currently available technology is the direct measurement of molecular oxygen in living tissue, a key component in cellular energy production. Here, we report on the development of a wireless wearable prototype for transcutaneous oxygenation monitoring based on quantifying the oxygen-dependent phosphorescence of a metalloporphyrin embedded within a highly breathable oxygen sensing film. The device is completely self-contained, weighs under 30 grams, performs on-board signal analysis, and can communicate with computers or smartphones. The wearable measures tissue oxygenation at the skin surface by detecting the lifetime and intensity of phosphorescence, which undergoes quenching in the presence of oxygen. As well as being insensitive to motion artifacts, it offers robust and reliable measurements even in variable atmospheric conditions related to temperature and humidity. Preliminary in vivo testing in a porcine ischemia model shows that the wearable is highly sensitive to changes in tissue oxygenation in the physiological range upon inducing a decrease in limb perfusion.

We demonstrate that shot noise in Fe=MgO=Fe=MgO=Fe double-barrier magnetic tunnel junctions is determined by the relative magnetic configuration of the junction and also by the asymmetry of the barriers. The proposed theoretical model, based on sequential tunneling through the system and including spin relaxation, successfully accounts for the experimental observations for bias voltages below 0.5 V, where the influence of quantum well states is negligible. A weak enhancement of conductance and shot noise, observed at some voltages (especially above 0.5 V), indicates the formation of quantum well states in the middle magnetic layer. As solid-state electronic devices shrink in size, further advances essentially depend on the understanding and control of spontaneous off-equilibrium fluctuations in charge and/or spin currents. Being a consequence of the discrete nature of charge carriers, shot noise (SN) is the only contribution to the noise which survives at low temperatures. Moreover, SN is an excellent tool to investigate the correlations and coherency at the nanoscale, well beyond the capabilities of electron transport [1][2][3][4][5][6][7][8][9]. In the absence of correlations, SN is Poissonian (full shot noise) and its noise power is given by S full ¼ 2eI, where I is the average current and e the electron charge. The Fano factor, F ¼ S exp =S full , represents the experimental SN normalized by the full SN value. It is generally suppressed (F < 1) by electron correlations [1] (quantum and/or Coulomb), but it can also be enhanced (F > 1), e.g., due to tunneling via localized states [10].After the observation of spin dependent transport in Fe=MgO=Fe magnetic tunnel junctions (MTJs) [11,12], MgO-based junctions became important elements of spintronic devices. Moreover, the recent implementation of MgO for an effective spin injection [13,14] revealed a new road for reducing the spin relaxation due to conductivity mismatch [15,16]. The efforts aimed at understanding spin coherency and SN, limited up to now to MTJs, revealed suppressed SN with Al 2 O 3 barriers (0:7 < F < 1) due to sequential tunneling [17] and also in serial MTJ arrays [18]. As for MTJs with MgO barriers, full SN (F ¼ 1) independent of the magnetic state was observed in epitaxial Fe=MgO=Fe [19]. Then, the noise was examined for ultrathin (less than 1 nm) MgO barriers, where F ' 0:92 was observed in the parallel state [20,21]. Double-barrier magnetic tunnel junctions (DMTJs), with either nanoparticles [22,23] or a continuous magnetic layer as the central electrode [24], have some advantages in comparison with MTJs. First, they show an enhanced tunnel magnetoresistance (TMR) [24,25], which additionally reveals oscillations induced by quantum well states (QWSs) [23,26]. Second, spin accumulation in the central layer is expected to substantially enhance spin torque [27,28]. The investigation of the statistics of spin tunneling events in hybrid spintronic devices is of great potential interest also beyond the spintronics community. From a general point o...