J. Albino Aguiar

Bio: J. Albino Aguiar is an academic researcher from Federal University of Pernambuco. The author has contributed to research in topics: Superconductivity & Vortex. The author has an hindex of 18, co-authored 148 publications receiving 1385 citations.

Screening of pair fluctuations in superconductors with coupled shallow and deep bands: A route to higher-temperature superconductivity

Abstract: A combination of strong Cooper pairing and weak superconducting fluctuations is crucial to achieve and stabilize high-${T}_{c}$ superconductivity. We demonstrate that a coexistence of a shallow carrier band with strong pairing and a deep band with weak pairing, together with the Josephson-like pair transfer between the bands to couple the two condensates, realizes an optimal multicomponent superconductivity regime: it preserves strong pairing to generate large gaps and a very high critical temperature but screens the detrimental superconducting fluctuations, thereby suppressing the pseudogap state. Surprisingly, we find that the screening is very efficient even when the interband coupling is very small. Thus, a multiband superconductor with a coherent mixture of condensates in the BCS regime (deep band) and in the BCS-BEC crossover regime (shallow band) offers a promising route to higher critical temperatures.

Superconductivity between standard types: Multiband versus single-band materials

Abstract: In the nearest vicinity of the critical temperature, types I and II of conventional single-band superconductors interchange at the Ginzburg-Landau parameter $\ensuremath{\kappa}=1/\sqrt{2}$. At lower temperatures this point unfolds into a narrow but finite interval of $\ensuremath{\kappa}$'s, shaping an intertype (transitional) domain in the $(\ensuremath{\kappa},T)$ plane. In the present work, based on the extended Ginzburg-Landau formalism, we show that the same picture of the two standard types with the transitional domain in between applies also to multiband superconductors. However, the intertype domain notably widens in the presence of multiple bands and can become extremely large when the system has a significant disparity between the band parameters. It is concluded that many multiband superconductors, such as recently discovered borides and iron-based materials, can belong to the intertype regime.

31p-S-4 Giant Magnetoresistance in Magnetic Manganese Oxide with Intrinsic Antiferromagnetic Spin Structure

Abstract: Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure. We ascribe this magnetoresistance to spin‐dependent electron scattering due to spin canting of the manganese oxide.

Laser Synthesis and Processing of Colloids: Fundamentals and Applications

Abstract: Driven by functionality and purity demand for applications of inorganic nanoparticle colloids in optics, biology, and energy, their surface chemistry has become a topic of intensive research interest. Consequently, ligand-free colloids are ideal reference materials for evaluating the effects of surface adsorbates from the initial state for application-oriented nanointegration purposes. After two decades of development, laser synthesis and processing of colloids (LSPC) has emerged as a convenient and scalable technique for the synthesis of ligand-free nanomaterials in sealed environments. In addition to the high-purity surface of LSPC-generated nanoparticles, other strengths of LSPC include its high throughput, convenience for preparing alloys or series of doped nanomaterials, and its continuous operation mode, suitable for downstream processing. Unscreened surface charge of LSPC-synthesized colloids is the key to achieving colloidal stability and high affinity to biomolecules as well as support materials,...

Sliding Friction-Physical Principles and Applications

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Nanostructured copper oxide semiconductors: a perspective on materials, synthesis methods and applications

Abstract: The oxides of copper (CuxO) are fascinating materials due to their remarkable optical, electrical, thermal and magnetic properties. Nanostructuring of CuxO can further enhance the performance of this important functional material and provide it with unique properties that do not exist in its bulk form. Three distinctly different phases of CuxO, mainly CuO, Cu2O and Cu4O3, can be prepared by numerous synthesis techniques including, vapour deposition and liquid phase chemical methods. In this article, we present a review of nanostructured CuxO focusing on their material properties, methods of synthesis and an overview of various applications that have been associated with nanostructured CuxO.

Superparamagnetic nanoparticles as versatile carriers and supporting materials for enzymes

Abstract: Enzymes are highly efficient catalysts extensively employed in biotechnology. Among the many challenging aspects in this area, enzymes are yet difficult to obtain and purify, which makes them extremely expensive. Therefore, the industrial use of such expensive biocatalysts suffers from a critical point, which is the lack of efficient recovery processes. As a very promising strategy, superparamagnetic nanoparticles based on magnetite (Fe3O4) and maghemite (γ-Fe2O3) have been recently employed as supporting materials for enzymes, exhibiting striking characteristics, such as large surface area, mobility and high mass transference. More than that, they can be easily recovered by applying an external magnetic field. In addition to their excellent environmental compatibility, the use of such superparamagnetic nanoparticles represents an effective green chemistry approach, since it prolongs, through the successive recovery cycles, the useful lifetime of the biocatalyst. Several enzymes and biomolecules, including antibodies, albumin, α-chymotrypsin, aminopeptidase, acetylcholine esterase, amylase, amyloglucosidase, celullase, epoxide hydrolases, esterase, lipase, lysozyme, pectinases, phosphatase, pyruvate phosphate dikinase, trypsin, subtilisin, urease, chitosanase, haloalkane dehalogenase, RNA polymerase, lactate dehydrogenase, alcohol dehydrogenase, galactosidase, catalase, cholesterol oxidase, d -amino acid oxidase, cathecol dioxygenase, fructosyl amino acid oxidase, l -lactate dehydrogenase, xanthine oxidase, glucose oxidase, glucosidase, laccase, peroxidases, tyrosinase and so on, have been successfully immobilized onto magnetic nanoparticles, and the recent progress in this area is focused on this review.