Tuning the superconducting performance of YBa2Cu3O7-δ films through field-induced oxygen doping.

The exploration of metal-insulator transitions to produce field-induced reversible resistive switching effects has been a longstanding pursuit in materials science. Although the resistive switching effect in strongly correlated oxides is often associated with the creation or annihilation of oxygen vacancies, the underlying mechanisms behind this phenomenon are complex and, in many cases, still not clear. This study focuses on the analysis of the superconducting performance of cuprate YBa2Cu3O7-δ (YBCO) devices switched to different resistive states through gate voltage pulses. The goal is to evaluate the effect of field-induced oxygen diffusion on the magnetic field and angular dependence of the critical current density and identify the role of induced defects in the switching performance. Transition electron microscopy measurements indicate that field-induced transition to high resistance states occurs through the generation of YBa2Cu4O7 (Y124) intergrowths with a large amount of oxygen vacancies, in agreement with the obtained critical current density dependences. These results have significant implications for better understanding the mechanisms of field-induced oxygen doping in cuprate superconductors and their role on the superconducting performance.

Correction to "Chemical Synthesis of La0.75Sr0.25CrO3 Thin Films for p-Type Transparent Conducting Electrodes".

[This corrects the article DOI: 10.1021/acs.chemmater.2c03831.].

Perturbed epigenetic transcriptional regulation in AML with IDH mutations causes increased susceptibility to NK cells.

Isocitrate dehydrogenase (IDH) mutations are found in 20% of acute myeloid leukemia (AML) patients. However, only 30-40% of the patients respond to IDH inhibitors (IDHi). We aimed to identify a molecular vulnerability to tailor novel therapies for AML patients with IDH mutations. We characterized the transcriptional and epigenetic landscape with the IDH2i AG-221, using an IDH2 mutated AML cell line model and AML patient cohorts, and discovered a perturbed transcriptional regulatory network involving myeloid transcription factors that were partly restored after AG-221 treatment. In addition, hypermethylation of the HLA cluster caused a down-regulation of HLA class I genes, triggering an enhanced natural killer (NK) cell activation and an increased susceptibility to NK cell-mediated responses. Finally, analyses of DNA methylation data from IDHi-treated patients showed that non-responders still harbored hypermethylation in HLA class I genes. In conclusion, this study provides new insights suggesting that IDH mutated AML is particularly sensitive to NK cell-based personalized immunotherapy.

Chemical Synthesis of La0.75Sr0.25CrO3 Thin Films for p-Type Transparent Conducting Electrodes.

The imperative need for highly performant and stable p-type transparent electrodes based on abundant metals is stimulating the research on perovskite oxide thin films. Moreover, exploring the preparation of these materials with the use of cost-efficient and scalable solution-based techniques is a promising approach to extract their full potential. Herein, we present the design of a chemical route, based on metal nitrate precursors, for the preparation of pure phase La0.75Sr0.25CrO3 (LSCO) thin films to be used as a p-type transparent conductive electrode. Different solution chemistries have been evaluated to ultimately obtain dense, epitaxial, and almost relaxed LSCO films. Optical characterization of the optimized LSCO films reveals promising high transparency with ∼67% transmittance while room temperature resistivity values are 1.4 Ω·cm. It is suggested that the presence of structural defects, i.e., antiphase boundaries and misfit dislocations, affects the electrical behavior of LSCO films. Monochromated electron energy loss spectroscopy allowed changes in the electronic structure in LSCO films to be determined, revealing the creation of Cr4+ and unoccupied states at the O 2p upon Sr-doping. This work offers a new venue to prepare and further investigate cost-effective functional perovskite oxides with potential to be used as p-type transparent conducting electrodes and be easily integrated in many oxide heterostructures.

A comparison of digital and conventional fabrication techniques for an esthetic maxillofacial prosthesis for the cheek and lip.

Maxillofacial prostheses have traditionally been manufactured by pouring silicone into molds. However, the development of computer-aided design and computer-aided manufacturing (CAD-CAM) systems allows the virtual planning, design, and manufacture of maxillofacial prostheses through the direct 3-dimensional printing of silicone. This clinical report describes the digital workflow as an alternative to the conventional method of restoring a large midfacial defect in the right cheek and lip. In addition, the approaches were nonblinded evaluated in relation to outcomes and time efficiency, while marginal adaptation and esthetics, including patient satisfaction, were assessed for both prostheses fabricated. The digital prosthesis had acceptable esthetics and fit with improved patient satisfaction, especially in terms of efficiency, comfort, and speed of the digital workflow.

High-harmonic spectroscopy of quantum phase transitions in a high-Tc superconductor.

We report on the nonlinear optical signatures of quantum phase transitions in the high-temperature superconductor YBCO, observed through high harmonic generation. While the linear optical response of the material is largely unchanged when cooling across the phase transitions, the nonlinear optical response sensitively imprints two critical points, one at the critical temperature of the cuprate with the exponential growth of the surface harmonic yield in the superconducting phase and another critical point, which marks the transition from strange metal to pseudogap phase. To reveal the underlying microscopic quantum dynamics, a strong-field quasi-Hubbard model was developed, which describes the measured optical response dependent on the formation of Cooper pairs. Further, the theory provides insight into the carrier scattering dynamics and allows us to differentiate between the superconducting, pseudogap, and strange metal phases. The direct connection between nonlinear optical response and microscopic dynamics provides a powerful methodology to study quantum phase transitions in correlated materials. Further implications are light wave control over intricate quantum phases, light-matter hybrids, and application for optical quantum computing.

Interarch space assessment in edentulous patients rehabilitated with complete removable dentures using open-access software.

BACKGROUND: The interarch space is defined as the vertical space between the edentulous ridge and the occlusal or incisal aspect of the opposing arch. Measuring the interarch space in a patient requiring an implant-supported fixed prosthesis is crucial for determining the prostheses to be used in each clinical situation. Depending on the measurements and other factors, such as the need for lip support or pink esthetics issues, decisions about the most convenient type of implant-supported prosthesis can be taken. Analogic workflow to measure the interarch space can represent a time-consuming and expensive procedure that may lead to inaccuracies. OBJECTIVE: To describe a step-by-step protocol to measure the upper and lower interarch space with open-access software, starting from the digital scan of the patient's complete dentures obtained with an intraoral scanner. METHODS: An extraoral scan (using an intraoral scanner) of the existing complete removable prosthesis is required to assess the interarch space for making an implant-supported prosthesis treatment planning. If the existing complete denture does not fulfill the required functional and esthetic parameters, a complete interim denture, a wax trial denture, or a printed denture prototype should be previously fabricated. The antagonist arch and the intermaxillary record scan also need to be obtained. Finally, all STL files are imported into an open-access software for measuring the interarch space. RESULTS: Open-source software can be used to measure the upper and lower interarch space from existing complete dentures following the step-by-step protocol outlined in this paper. CONCLUSION: Interarch space of edentulous patients rehabilitated with complete dentures can be measured with a 360 degrees scanning of the existing complete denture and open-access software by applying the protocol outlined in this paper. CLINICAL RELEVANCE: The clinician can assess and digitally measure the interarch space of edentulous patients requiring an implant-supported fixed prosthesis using an open access software.

Luminescent and Magnetic Tb-MOF Flakes Deposited on Silicon.

The synthesis of a terbium-based 2D metal-organic framework (MOF), of formula [Tb(MeCOO)(PhCOO)2] (1), a crystalline material formed by neutral nanosheets held together by Van der Waals interactions, is presented. The material can be easily exfoliated by sonication and deposited onto different substrates. Uniform distributions of Tb-2D MOF flakes onto silicon were obtained by spin-coating. We report the luminescent and magnetic properties of the deposited flakes compared with those of the bulk. Complex 1 is luminescent in the visible and has a sizeable quantum yield of QY = 61% upon excitation at 280 nm. Photoluminescence measurements performed using a micro-Raman set up allowed us to characterize the luminescent spectra of individual flakes on silicon. Magnetization measurements of flakes-on-silicon with the applied magnetic field in-plane and out-of-plane display anisotropy. Ac susceptibility measurements show that 1 in bulk exhibits field-induced slow relaxation of the magnetization through two relaxation paths and the slowest one, with a relaxation time of τlf ≈ 0.5 s, is assigned to a direct process mechanism. The reported exfoliation of lanthanide 2D-MOFs onto substrates is an attractive approach for the development of multifunctional materials and devices for different applications.

Challenging conventional karyotyping by next-generation karyotyping in 281 intensively treated patients with AML.

Although copy number alterations (CNAs) and translocations constitute the backbone of the diagnosis and prognostication of acute myeloid leukemia (AML), techniques used for their assessment in routine diagnostics have not been reconsidered for decades. We used a combination of 2 next-generation sequencing-based techniques to challenge the currently recommended conventional cytogenetic analysis (CCA), comparing the approaches in a series of 281 intensively treated patients with AML. Shallow whole-genome sequencing (sWGS) outperformed CCA in detecting European Leukemia Net (ELN)-defining CNAs and showed that CCA overestimated monosomies and suboptimally reported karyotype complexity. Still, the concordance between CCA and sWGS for all ELN CNA-related criteria was 94%. Moreover, using in silico dilution, we showed that 1 million reads per patient would be enough to accurately assess ELN-defining CNAs. Total genomic loss, defined as a total loss ≥200 Mb by sWGS, was found to be a better marker for genetic complexity and poor prognosis compared with the CCA-based definition of complex karyotype. For fusion detection, the concordance between CCA and whole-transcriptome sequencing (WTS) was 99%. WTS had better sensitivity in identifying inv(16) and KMT2A rearrangements while showing limitations in detecting lowly expressed PML-RARA fusions. Ligation-dependent reverse transcription polymerase chain reaction was used for validation and was shown to be a fast and reliable method for fusion detection. We conclude that a next-generation sequencing-based approach can replace conventional CCA for karyotyping, provided that efforts are made to cover lowly expressed fusion transcripts.

The comparative agendas project in Latin America: data and coding / Comparative Agendas Project en América Latina: datos y codificación / O Comparative Agendas Project na América Latina: dados e codificação

Abstract This paper introduces the Comparative Agendas Project system of coding as well as a wealth of gathered and in process data from Latin America using this established and reliable system for capturing policy attention comparatively and over time. While this is not the first introduction of the coding system, it is the first introduction aimed at Latin America and a new type of political system beyond North American and European democracies. First, we present an overview of the Comparative Agendas Project (CAP) and the Master Codebook used to create comparative policy attention data across countries, over time, and between agendas. These details of CAP are discussed for Latin America in general and for Brazil, Colombia and Ecuador, countries that recently started to gather data using these coding.

Resumen: Este artículo presenta el sistema de codificación del Comparative Agendas Project, que es capaz de capturar la atención política de manera comparada y a lo largo del tiempo. Presenta también una amplia gama de datos recogidos y procesados en América Latina, sobre la base de este consolidado y fiable sistema de codificación. Aunque no sea un sistema inédito, esta es la primera vez que se introduce en América Latina y en un tipo de sistema político diferente del que se observa en las democracias de América do Norte y Europa. Para ello, ofrecemos una descripción del Comparative Agendas Project y de su libro de códigos (Master Codebook), usado para obtener datos de atención política de forma comparada entre países y distintos tipos de agendas a lo largo del tiempo. Esos detalles se discuten en relación con América Latina en general y con el contexto nacional de Brasil, Colombia y Ecuador, países de la región que cuentan con el primer conjunto de datos recogidos con ese sistema de codificación.

Resumo Esse artigo apresenta o sistema de codificação do Comparative Agendas Project, que é capaz de capturar a atenção política de maneira comparada e ao longo do tempo. Apresenta também uma ampla gama de dados coletados e em processamento na América Latina, já usando esse consolidado e confiável sistema de codificação. Embora não seja um sistema inédito, essa é a primeira vez que está sendo introduzido na América Latina e em um tipo de sistema político diferente do que se observa nas democracias da América do Norte e da Europa. Para isso, oferecemos um panorama do Comparative Agendas Project e de seu livro de códigos (Master Codebook), usado para obter dados de atenção política de forma comparada entre os países e suas agendas, ao longo do tempo. Esses detalhes são discutidos em relação a América Latina em geral e ao contexto nacional do Brasil, Colômbia e Equador, países da região que contam com a primeira leva de dados processados com esse sistema de codificação.

Direct Visualization of Current-Stimulated Oxygen Migration in YBa2Cu3O7-δ Thin Films.

The past years have witnessed major advancements in all-electrical doping control on cuprates. In the vast majority of cases, the tuning of charge carrier density has been achieved via electric field effect by means of either a ferroelectric polarization or using a dielectric or electrolyte gating. Unfortunately, these approaches are constrained to rather thin superconducting layers and require large electric fields in order to ensure sizable carrier modulations. In this work, we focus on the investigation of oxygen doping in an extended region through current-stimulated oxygen migration in YBa2Cu3O7-δ superconducting bridges. The underlying methodology is rather simple and avoids sophisticated nanofabrication process steps and complex electronics. A patterned multiterminal transport bridge configuration allows us to electrically assess the directional counterflow of oxygen atoms and vacancies. Importantly, the emerging propagating front of current-dependent doping δ is probed in situ by optical microscopy and scanning electron microscopy. The resulting imaging techniques, together with photoinduced conductivity and Raman scattering investigations, reveal an inhomogeneous oxygen vacancy distribution with a controllable propagation speed permitting us to estimate the oxygen diffusivity. These findings provide direct evidence that the microscopic mechanism at play in electrical doping of cuprates involves diffusion of oxygen atoms with the applied current. The resulting fine control of the oxygen content would permit a systematic study of complex phase diagrams and the design of electrically addressable devices.

Evaluación de las características clínicas y evolución de pacientes con COVID-19 a partir de una serie de 1000 pacientes atendidos en servicios de urgencias españoles / Analysis of clinical characteristics and outcomes in patients with COVID-19 based on a series of 1000 patients treated in Spanish emergency departments

OBJETIVO: Describir las características clínicas de los pacientes con COVID-19 atendidos en los servicios de urgencias hospitalarios (SUH) españoles y evaluar su asociación con los resultados de su evolución. MÉTODOS: Estudio multicéntrico, anidado en una cohorte prospectiva. Participaron 61 SUH que incluyeron pacientes seleccionados aleatoriamente de todos los diagnosticados de COVID-19 entre el 1 de marzo y el 30 de abril de 2020. Se recogieron características basales, clínicas, de exploraciones complementarias y terapéuticas del episodio en los SUH. Se calcularon las odds ratio (OR) asociadas a la mortalidad intrahospitalaria y al evento combinado formado por el ingreso en unidad de cuidados intensivos (UCI), la intubación orotraqueal o ventilación mecánica invasiva (IOT/ VMI), crudas y ajustadas con modelos de regresión logística para tres grupos de variables independientes: basales, clínicas y de exploraciones complementarias. RESULTADOS: La edad media fue de 62 años (DE 18). La mayoría manifestaron fiebre, tos seca, disnea, febrícula y diarrea. Las comorbilidades más frecuentes fueron las enfermedades cardiovasculares, seguidas de las respiratorias y el cáncer. Las variables basales que se asociaron independientemente y de forma directa a peores resultados evolutivos (tanto a mortalidad como a evento combinado) fueron edad y obesidad; las variables clínicas fueron disminución de consciencia y crepitantes a la auscultación pulmonar, y de forma inversa cefalea; y las variables de resultados de exploraciones complementarias fueron infiltrados pulmonares bilaterales y cardiomegalia radiológicos, y linfopenia, hiperplaquetosis, dímero-D > 500 mg/dL y lactato-deshidrogenasa > 250 UI/L en la analítica. CONCLUSIONES: Conocer las características clínicas y la comorbilidad de los pacientes con COVID-19 atendidos en urgencias permite identificar precozmente a la población más susceptible de empeorar, para prever y mejorar los resultados

OBJECTIVES: To describe the clinical characteristics of patients with coronavirus disease 2019 (COVID-19) treated in hospital emergency departments (EDs) in Spain, and to assess associations between characteristics and outcomes. METHODS: Prospective, multicenter, nested-cohort study. Sixty-one EDs included a random sample of all patients diagnosed with COVID-19 between March 1 and April 30, 2020. Demographic and baseline health information, including concomitant conditions; clinical characteristics related to the ED visit and complementary test results; and treatments were recorded throughout the episode in the ED. We calculated crude and adjusted odds ratios for risk of in-hospital death and a composite outcome consisting of the following events: intensive care unit admission, orotracheal intubation or mechanical ventilation, or in-hospital death. The logistic regression models were constructed with 3 groups of independent variables: the demographic and baseline health characteristics, clinical characteristics and complementary test results related to the ED episode, and treatments. RESULTS: The mean (SD) age of patients was 62 (18) years. Most had high- or low-grade fever, dry cough, dyspnea, and diarrhea. The most common concomitant conditions were cardiovascular diseases, followed by respiratory diseases and cancer. Baseline patient characteristics that showed a direct and independent association with worse outcome (death and the composite outcome) were age and obesity. Clinical variables directly associated with worse outcomes were impaired consciousness and pulmonary crackles; headache was inversely associated with worse outcomes. Complementary test findings that were directly associated with outcomes were bilateral lung infiltrates, lymphopenia, a high platelet count, a D-dimer concentration over 500 mg/dL, and a lactate-dehydrogenase concentration over 250 IU/L in blood. CONCLUSION: This profile of the clinical characteristics and comorbidity of patients with COVID-19 treated in EDs helps us predict outcomes and identify cases at risk of exacerbation. The information can facilitate preventive measures and improve outcomes

Analysis of clinical characteristics and outcomes in patients with COVID-19 based on a series of 1000 patients treated in Spanish emergency departments. / Evaluación de las características clínicas y evolución de pacientes con COVID-19 a partir de una serie de 1000 pacientes atendidos en servicios de urgencias españoles.

OBJECTIVES: To describe the clinical characteristics of patients with coronavirus disease 2019 (COVID-19) treated in hospital emergency departments (EDs) in Spain, and to assess associations between characteristics and outcomes. MATERIAL AND METHODS: Prospective, multicenter, nested-cohort study. Sixty-one EDs included a random sample of all patients diagnosed with COVID-19 between March 1 and April 30, 2020. Demographic and baseline health information, including concomitant conditions; clinical characteristics related to the ED visit and complementary test results; and treatments were recorded throughout the episode in the ED. We calculated crude and adjusted odds ratios for risk of in-hospital death and a composite outcome consisting of the following events: intensive care unit admission, orotracheal intubation or mechanical ventilation, or in-hospital death. The logistic regression models were constructed with 3 groups of independent variables: the demographic and baseline health characteristics, clinical characteristics and complementary test results related to the ED episode, and treatments. RESULTS: The mean (SD) age of patients was 62 (18) years. Most had high- or low-grade fever, dry cough, dyspnea, and diarrhea. The most common concomitant conditions were cardiovascular diseases, followed by respiratory diseases and cancer. Baseline patient characteristics that showed a direct and independent association with worse outcome (death and the composite outcome) were age and obesity. Clinical variables directly associated with worse outcomes were impaired consciousness and pulmonary crackles; headache was inversely associated with worse outcomes. Complementary test findings that were directly associated with outcomes were bilateral lung infiltrates, lymphopenia, a high platelet count, a D-dimer concentration over 500 mg/dL, and a lactate-dehydrogenase concentration over 250 IU/L in blood. CONCLUSION: This profile of the clinical characteristics and comorbidity of patients with COVID-19 treated in EDs helps us predict outcomes and identify cases at risk of exacerbation. The information can facilitate preventive measures and improve outcomes.

OBJETIVO: Describir las características clínicas de los pacientes con COVID-19 atendidos en los servicios de urgencias hospitalarios (SUH) españoles y evaluar su asociación con los resultados de su evolución. METODO: Estudio multicéntrico, anidado en una cohorte prospectiva. Participaron 61 SUH que incluyeron pacientes seleccionados aleatoriamente de todos los diagnosticados de COVID-19 entre el 1 de marzo y el 30 de abril de 2020. Se recogieron características basales, clínicas, de exploraciones complementarias y terapéuticas del episodio en los SUH. Se calcularon las odds ratio (OR) asociadas a la mortalidad intrahospitalaria y al evento combinado formado por el ingreso en unidad de cuidados intensivos (UCI), la intubación orotraqueal o ventilación mecánica invasiva (IOT/ VMI), crudas y ajustadas con modelos de regresión logística para tres grupos de variables independientes: basales, clínicas y de exploraciones complementarias. RESULTADOS: La edad media fue de 62 años (DE 18). La mayoría manifestaron fiebre, tos seca, disnea, febrícula y diarrea. Las comorbilidades más frecuentes fueron las enfermedades cardiovasculares, seguidas de las respiratorias y el cáncer. Las variables basales que se asociaron independientemente y de forma directa a peores resultados evolutivos (tanto a mortalidad como a evento combinado) fueron edad y obesidad; las variables clínicas fueron disminución de consciencia y crepitantes a la auscultación pulmonar, y de forma inversa cefalea; y las variables de resultados de exploraciones complementarias fueron infiltrados pulmonares bilaterales y cardiomegalia radiológicos, y linfopenia, hiperplaquetosis, dímero-D > 500 mg/dL y lactato-deshidrogenasa > 250 UI/L en la analítica. CONCLUSIONES: Conocer las características clínicas y la comorbilidad de los pacientes con COVID-19 atendidos en urgencias permite identificar precozmente a la población más susceptible de empeorar, para prever y mejorar los resultados.

Nanoscale Correlations between Metal-Insulator Transition and Resistive Switching Effect in Metallic Perovskite Oxides.

Strongly correlated perovskite oxides are a class of materials with fascinating intrinsic physical functionalities due to the interplay of charge, spin, orbital ordering, and lattice degrees of freedom. Among the exotic phenomena arising from such an interplay, metal-insulator transitions (MITs) are fundamentally still not fully understood and are of large interest for novel nanoelectronics applications, such as resistive switching-based memories and neuromorphic computing devices. In particular, rare-earth nickelates and lanthanum strontium manganites are archetypical examples of bandwidth-controlled and band-filling-controlled MIT, respectively, which are used in this work as a playground to correlate the switching characteristics of the oxides and their MIT properties by means of local probe techniques in a systematic manner. These findings suggest that an electric-field-induced MIT can be triggered in these strongly correlated systems upon generation of oxygen vacancies and establish that lower operational voltages and larger resistance ratios are obtained in those films where the MIT lies closer to room temperature. This work demonstrates the potential of using MITs in the next generation of nanoelectronics devices.

Multi-terminal Transistor-like Devices Based on Strongly Correlated Metallic Oxides for Neuromorphic Applications.

Memristive devices are attracting a great attention for memory, logic, neural networks, and sensing applications due to their simple structure, high density integration, low-power consumption, and fast operation. In particular, multi-terminal structures controlled by active gates, able to process and manipulate information in parallel, would certainly provide novel concepts for neuromorphic systems. In this way, transistor-based synaptic devices may be designed, where the synaptic weight in the postsynaptic membrane is encoded in a source-drain channel and modified by presynaptic terminals (gates). In this work, we show the potential of reversible field-induced metal-insulator transition (MIT) in strongly correlated metallic oxides for the design of robust and flexible multi-terminal memristive transistor-like devices. We have studied different structures patterned on YBa2Cu3O7-δ films, which are able to display gate modulable non-volatile volume MIT, driven by field-induced oxygen diffusion within the system. The key advantage of these materials is the possibility to homogeneously tune the oxygen diffusion not only in a confined filament or interface, as observed in widely explored binary and complex oxides, but also in the whole material volume. Another important advantage of correlated oxides with respect to devices based on conducting filaments is the significant reduction of cycle-to-cycle and device-to-device variations. In this work, we show several device configurations in which the lateral conduction between a drain-source channel (synaptic weight) is effectively controlled by active gate-tunable volume resistance changes, thus providing the basis for the design of robust and flexible transistor-based artificial synapses.

A regulatory role for CHD2 in myelopoiesis.

The transcriptional program that dictates haematopoietic cell fate and differentiation requires an epigenetic regulatory and memory function, provided by a network of epigenetic factors that regulate DNA methylation, post-translational histone modifications and chromatin structure. Disturbed epigenetic regulation causes perturbations in the blood cell differentiation program that results in various types of haematopoietic disorders. Thus, accurate epigenetic regulation is essential for functional haematopoiesis. In this study, we used a CRISPR-Cas9 screening approach to identify new epigenetic regulators in myeloid differentiation. We designed a Chromatin-UMI CRISPR guide library targeting 1092 epigenetic regulators. Phorbol 12-myristate 13-acetate (PMA) treatment of the chronic myeloid leukaemia cell line K-562 was used as a megakaryocytic myeloid differentiation model. Both previously described developmental epigenetic regulators and novel factors were identified in our screen. In this study, we validated and characterized a role for the chromatin remodeller CHD2 in myeloid proliferation and megakaryocytic differentiation.

Suppression of superconductivity at the nanoscale in chemical solution derived YBa2Cu3O7-δ thin films with defective Y2Ba4Cu8O16 intergrowths.

The analysis of the microstructure and superconducting behavior of chemical solution deposited epitaxial YBa2Cu3O7-δ films, with thickness going down to 5 nm has been carried out with the purpose to disclose the behavior of the most common intergrowth in these films, the Y2Ba4Cu8O16. The analysis of ultrathin films is a unique opportunity to investigate the superconducting behavior of these nanoscale defects because of the high concentration created as a consequence of the elastic energy associated to the misfit strain. Magnetic susceptibility and X-ray diffraction measurements evidence a strong decrease of the superconducting volume correlated with an increase of the intergrowth volume fraction. We demonstrate that these intergrowths are non-superconducting nanoscale regions where Cooper pair formation is disrupted, in agreement with their key role as artificial pinning centers for vortices in YBa2Cu3O7-δ films and coated conductors.

Depairing Current at High Magnetic Fields in Vortex-Free High-Temperature Superconducting Nanowires.

Superconductors are essential in many present and future technologies, from large-scale devices for medical imaging, accelerators, or fusion experiments to ultra-low-power superconducting electronics. However, their potential applicability, and particularly that of high-temperature superconductors (HTS), is severely affected by limited performances at large magnetic fields and high temperatures, where their use is most needed. One of the main reasons for these limitations is the presence of quantized vortices, whose movements result in losses, internal noise, and reduced performances. The conventional strategy to overcome the flow of vortices is to pin them along artificial defects. Here, we theoretically and experimentally demonstrate that critical-current density in high-temperature superconductors can reach unprecedented high values at high fields and temperatures by preventing vortex entry. By tailoring the geometry, that is, reducing the width, W, of nanowire-patterned HTS films, the range of the Meissner state, for which no vortices are present, is extended up to very large applied field values, on the order of ∼1 T. Current densities on the order of the depairing current can be sustained under high fields for a wide range of temperatures. Results may be relevant both for devising new conductors carrying depairing-current values at high temperatures and large magnetic fields and for reducing flux noise in sensors and quantum systems.

Control of nanostructure and pinning properties in solution deposited YBa2Cu3O7-x nanocomposites with preformed perovskite nanoparticles.

Solution deposited YBa2Cu3O7-x (YBCO) nanocomposites with preformed nanoparticles represent a promising cost-effective approach for superior critical current properties under applied magnetic fields. Nonetheless, the majority of YBCO nanocomposites with high nanoparticle loads (>20%) suffer from nanoparticle coalescence and degraded superconducting properties. Here, we study the influence of nanoparticle concentration (0-25% mol), size (5 nm-10 nm) and composition (BaHfO3, BaZrO3) on the generation of structural defects in the epitaxial YBCO matrix, key parameter for vortex pinning. We demonstrate that flash-heated superconducting nanocomposites with 20 mol% preformed BaHfO3 or BaZrO3 perovskite secondary phases feature discrete and small (7 nm) nanoparticles and high density of YBa2Cu4O8 (Y248) intergrowths. We identify a synergy between Y248 intergrowth density and small nanoparticles to increase artificial vortex pinning centers. Also, we validate the multideposition process to successfully increase film thickness of epitaxial nanocomposites with competitive critical currents Ic at 77 K.

Electrochemical Tuning of Metal Insulator Transition and Nonvolatile Resistive Switching in Superconducting Films.

Modulation of carrier concentration in strongly correlated oxides offers the unique opportunity to induce different phases in the same material, which dramatically change their physical properties, providing novel concepts in oxide electronic devices with engineered functionalities. This work reports on the electric manipulation of the superconducting to insulator phase transition in YBa2Cu3O7-δ thin films by electrochemical oxygen doping. Both normal state resistance and the superconducting critical temperature can be reversibly manipulated in confined active volumes of the film by gate-tunable oxygen diffusion. Vertical and lateral oxygen mobility may be finely modulated, at the micro- and nano-scale, by tuning the applied bias voltage and operating temperature thus providing the basis for the design of homogeneous and flexible transistor-like devices with loss-less superconducting drain-source channels. We analyze the experimental results in light of a theoretical model, which incorporates thermally activated and electrically driven volume oxygen diffusion.