Analysis and performance of lumped-element kinetic inductance detectors for W-band

Lumped-element superconducting resonators are a promising technology for their use in millimeter-wave observations and quantum computing applications that require large arrays of extremely sensitive detectors. Among them, lumped-element kinetic inductance detectors (LEKIDs) have shown good performance in the submillimeter band in several earth-based telescopes. In this work, LEKIDs for their use as millimeter-wave receivers of astronomical applications are presented. LEKID arrays using a thin bilayer of superconducting titanium/aluminum (Ti/Al), deposited on the silicon substrate, have been designed and fabricated. The design of a dual-polarization LEKID with the goal of detection at the W -band for two orthogonal polarizations is described and a fabricated array has demonstrated absorption at ambient temperature. Also, an approximate design methodology of the coupling parameter for LEKIDs' readout, essential for dynamic range optimization of the detector under millimeter-wave radiation, is proposed. In addition, the resonance characteristics and coupling factor of the fabricated superconducting resonators using high-quality internal factor Qi under cryogenic temperatures have been analyzed. The design guidelines in this work are applicable to other LEKID arrays, and the presented superconducting Ti/Al thin-film LEKIDs can be used in future receiver arrays in the millimeter bands.This work was supported by Ministry of Science, Innovation and Universities under Grants ESP2017-83921-C2-2-R, ESP2017-86582-C4-1-R, ESP2017-86582-C4-3-R, ESP2017-92706-EXP, AYA2017-92153-EXP, “Severo Ochoa” Programme for Centres of Excellence in R&D (MINECO, Grant SEV-2016-0686). By Comunidad de Madrid under Grant P2018/NMT-4291. D.G. and A.G also acknowledge Grant DEFROST N62909-19-1-2053 from ONRGlobal. A.G. acknowledges IJCI-2017-33991

Bi-layer kinetic inductance detectors for W-band

An array of superconducting kinetic inductance detectors (KID) has been fabricated and it has demonstrated absorption at W-Band. The use of a bi-layer structure based on aluminum (AI) and titanium (Ti) shows a lower superconducting critical temperature (T c ), which allows the detection at W-band. A design methodology is presented taking into account the KID geometry in order to maximize the absorption and a dual-polarization KID has been designed using the proposed methodology. Two prototypes of KID on Silicon substrate have been fabricated showing a good agreement between measurement and simulation results. The measurements at room temperature from 65 to 110 GHz show the matching at the frequency band, while dark cryogenic characterization demonstrated the low frequency design.The authors acknowledge financial supports: Ministry of Science, Innovation and Universities Grants ESP2017-83921-C2-2-R, ESP2017-86582-C4-1-R, ESP2017-86582-C4-3-R, MAT2017-85617-R, ESP2017-92706-EXP, AYA2017-92153-EXP and from Comunidad de Madrid through Grant P2018/NMT-4291 TEC2-SPACE-CM. A.G. acknowledges IJCI-2017-33991; IMDEA Nanociencia acknowledges support from the “Severo Ochoa” Programme for Centres of Excellence in R&D (MINECO, Grant SEV-2016-0686). D.G. and A.G also acknowledge Grant DEFROST N62909-19-1-2053 from ONR-Global

Little–Parks effect governed by magnetic nanostructures with out-of-plane magnetization

Little–Parks effect names the oscillations in the superconducting critical temperature as a function of the magnetic field. This effect is related to the geometry of the sample. In this work, we show that this effect can be enhanced and manipulated by the inclusion of magnetic nanostructures with perpendicular magnetization. These magnetic nanodots generate stray fields with enough strength to produce superconducting vortex–antivortex pairs. So that, the L–P effect deviation from the usual geometrical constrictions is due to the interplay between local magnetic stray fields and superconducting vortices. Moreover, we compare our results with a low-stray field sample (i.e. with the dots in magnetic vortex state) showing how the enhancement of the L–P effect can be explained by an increment of the effective size of the nanodots.With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737

Realization of macroscopic ratchet effect based on nonperiodic and uneven potentials

Ratchet devices allow turning an ac input signal into a dc output signal. A ratchet device is set by moving particles driven by zero averages forces on asymmetric potentials. Hybrid nanostructures combining artificially fabricated spin ice nanomagnet arrays with superconducting films have been identified as a good choice to develop ratchet nanodevices. In the current device, the asymmetric potentials are provided by charged Néel walls located in the vertices of spin ice magnetic honeycomb array, whereas the role of moving particles is played by superconducting vortices. We have experimentally obtained ratchet effect for different spin ice I configurations and for vortex lattice moving parallel or perpendicular to magnetic easy axes. Remarkably, the ratchet magnitudes are similar in all the experimental runs; i. e. different spin ice I configurations and in both relevant directions of the vortex lattice motion. We have simulated the interplay between vortex motion directions and a single asymmetric potential. It turns out vortices interact with uneven asymmetric potentials, since they move with trajectories crossing charged Néel walls with different orientations. Moreover, we have found out the asymmetric pair potentials which generate the local ratchet effect. In this rocking ratchet the particles (vortices) on the move are interacting each other (vortex lattice); therefore, the ratchet local effect turns into a global macroscopic effect. In summary, this ratchet device benefits from interacting particles moving in robust and topological protected type I spin ice landscapes.This work was supported by Spanish MICINN grants FIS2016-76058 (AEI/FEDER, UE), EU COST- CA16218. IMDEA Nanociencia acknowledges support from the ‘Severo Ochoa’ Programme for Centres of Excellence in R&D (MICINN, Grant SEV-2016-0686). MCO and AG acknowledges financial support from Spanish MICINN Grant ESP2017-86582-C4-1-R and IJCI-2017-33991; AMN acknowledges financial support from Spanish CAM Grant 2018-T1/IND-10360. MV acknowledges financial support from Spanish MICINN Grant PID2019-104604RB/AEI/10.13039/50110001103.Peer reviewe

Magnetic multilayers with competing in plane and out of plane anisotropies

Resumen del póster presentado al 10th International Symposium on Metallic Multilayers (MML), celebrado en Madrid (España) del 17 al 21 de junio de 2019.Multilayers formed by layers with different anisotropy conform one of the most interesting kinds of magnetic multi-layered systems. In particular, multilayers combining films with in plane and out of plane anisotropy provide a wide range of magnetic properties depending on the dominant anisotropy and the degree of coupling between the layers. When employed as spacers, some metals can induce a strong modulation in the coupling, which can be controlled using different spacer thicknesses. Here, we report on a particular system consisting of a perpendicular magnetic anisotropy (PMA) [Co/Pd]n multilayer with an in-plane shape anisotropy Permalloy (Py) layer. Our multi-layered system is grown by sputtering and its magnetic properties studied by Magneto-optical Kerr effect (MOKE) and magnetic force microscopy (MFM). To achieve tuneable magnetization angles and tailor the degree of coupling, we employ a non- magnetic spacer of variable thickness (ruthenium). The PMA of the multilayers can be enhanced by increasing the number of units, adding an additional degree of freedom. In this study, we vary systematically the [Co/Pd]n multilayer structure and spacer thickness. The magnetic coupling is investigated combining magnetization measurements by MOKE at room temperature in longitudinal and polar configuration, thus measuring in plane and out of plane magnetization, with MFM to get the domain structure

Hybrid molecular graphene transistor as an operando and optoelectronic platform

International audienceLack of reproducibility hampers molecular devices integration into large-scale circuits. Thus, incorporating operando characterization can facilitate the understanding of multiple features producing disparities in different devices. In this work, we report the realization of hybrid molecular graphene field effect transistors (m-GFETs) based on 11-(Ferrocenyl)undecanethiol (FcC 11 SH) micro self-assembled monolayers (μSAMs) and high-quality graphene (Gr) in a back-gated configuration. On the one hand, Gr enables redox electron transfer, avoids molecular degradation and permits operando spectroscopy. On the other hand, molecular electrode decoration shifts the Gr Dirac point (V DP ) to neutrality and generates a photocurrent in the Gr electron conduction regime. Benefitting from this heterogeneous response, the m-GFETs can implement optoelectronic AND/OR logic functions. Our approach represents a step forward in the field of molecular scale electronics with implications in sensing and computing based on sustainable chemicals

New insights into the genetic etiology of Alzheimer’s disease and related dementias

Characterization of the genetic landscape of Alzheimer’s disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/‘proxy’ AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

New insights into the genetic etiology of Alzheimer’s disease and related dementias

Characterization of the genetic landscape of Alzheimer’s disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/‘proxy’ AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele