77 research outputs found
Giant Shapiro Steps in a Superconducting Network of Nanoscale Nb Islands
Recently, a dynamic vortex Mott transition has been observed in an array of superconducting nanodots. Here, we report the effect of the interaction of microwave radiation on this system and we show the occurrence of giant Shapiro steps
Correlated disorder in myelinated axons orientational geometry and structure
While the ultrastructure of the myelin has been considered to be a
quasi-crystalline stable system, nowadays its multiscale complex dynamics
appears to play a key role for its functionality, degeneration and repair
processes following neurological diseases and trauma. In this work, we have
investigated the axons interactions associated to the nerve functionality,
measuring the spatial distribution of the orientational fluctuations of axons
in a Xenopus Laevis sciatic nerve. At this aim, we have used Scanning micro
X-ray Diffraction (SmXRD), a non-invasive already applied to other
heterogeneous systems presenting complex geometries from microscale to
nanoscale. We have found that the orientational spatial fluctuations of fresh
axons show a correlated disorder described by Levy flight distribution. Thus,
we have studied how this correlated disorder evolves during the degeneration of
the nerve. Our results show that the spatial distribution of axons
orientational fluctuations in unfresh, aged nerve loose the correlated disorder
assuming a randomly disordered behaviour. This work allows a deeper
understanding of nerve states and paves the way to study other materials and
biomaterials with the same technique to detect and to characterize their states
and supramolecular structure, associated with dynamic structural changes at the
nanoscale and mesoscale.Comment: 9 pages, 4 figure
The Microstrain-Doping Phase Diagram of the Iron Pnictides Heterostructures at Atomic Limit
The 3D phase diagram of iron pnictides where the critical temperature depends
on charge density and microstrain in the active FeAs layers is proposed. The
iron pnictides superconductors are shown to be a practical realization of a
heterostructure at the atomic limit made of a superlattice of FeAs layers
intercalated by spacer layers. We have focussed our interest on the A 1-x
BxFe2As2 (122) families and we show that FeAs layers have a tensile microstrain
due to the misfit strain between the active layers and the spacers. We have
identified the critical range of doping and microstrain where the critical
temperature gets amplified to its maximum value.Comment: 5 pages, 3 figure
Misfit Strain in Superlattices Controlling the Electron-Lattice Interaction via Microstrain in Active Layers
High-temperature superconductivity (HTS) emerges in quite different electronic materials: cuprates, diborides, and iron-pnictide superconductors. Looking for unity in the diversity we find in all these materials a common lattice architecture: they are practical realizations of heterostructures at atomic limit made of superlattices of metallic active layers intercalated by spacers as predicted in 1993 by one of us. The multilayer architecture is the key feature for the presence of electronic topological transitions where the Fermi surface of one of the subbands changes dimensionality. The superlattice misfit strain between the active and spacer layers is shown to be a key variable to drive the system to the highest critical temperature that occurs at a particular point of the 3D phase diagram () where is the charge transfer or doping. The plots of as a function of misfit strain at constant charge transfer in cuprates show a first-order quantum critical phase transition where an itinerant striped magnetic phase competes with superconductivity in the proximity of a structural phase transition, that is, associated with an electronic topological transition. The shape resonances in these multigap superconductors is associated with the maximum
Far from Equilibrium Percolation, Stochastic and Shape Resonances in the Physics of Life
Key physical concepts, relevant for the cross-fertilization between condensed matter physics and the physics of life seen as a collective phenomenon in a system out-of-equilibrium, are discussed. The onset of life can be driven by: (a) the critical fluctuations at the protonic percolation threshold in membrane transport; (b) the stochastic resonance in biological systems, a mechanism that can exploit external and self-generated noise in order to gain efficiency in signal processing; and (c) the shape resonance (or Fano resonance or Feshbach resonance) in the association and dissociation processes of bio-molecules (a quantum mechanism that could play a key role to establish a macroscopic quantum coherence in the cell)
Manifestation of percolation in high temperature superconductivity
Emergent advanced electronic and magnetic functionalities in novel materials appear in systems with a complex lattice structure. The key point is understanding the intrinsic effect of lattice fluctuations on the relevant electronic features in the range of 10–100 meV near the Fermi level in new materials which is needed to develop advanced quantum nano-devices. This requires the control of structural inhomogeneity at multiple scales. Here we report some of the known advances in the field of percolative superconductivity. The necessity of the review is based on the growing consensus that the lack of an understanding of high temperature superconductivity is due to the few information on lattice fluctuations. In particular they could control the pseudo-gap phase, the electronic duality of holes in Fermi arcs and electrons in small Fermi pockets, multiple condensates in different points of the k-space. Moreover the emerging lattice granularity in cuprates shifts the search for the superconducting mechanism from a homogeneous superconductivity to a percolative superconductivity, therefore it is the scope of this review to provide further data to this kind of research
Manipulating electronic states at oxide interfaces using focused micro X-rays from standard lab-sources
Recently, x-ray illumination, using synchrotron radiation, has been used to
manipulate defects, stimulate self-organization and to probe their structure.
Here we explore a method of defect-engineering low-dimensional systems using
focused laboratory-scale X-ray sources. We demonstrate an irreversible change
in the conducting properties of the 2-dimensional electron gas at the interface
between the complex oxide materials LaAlO3 and SrTiO3 by X-ray irradiation. The
electrical resistance is monitored during exposure as the irradiated regions
are driven into a high resistance state. Our results suggest attention shall be
paid on electronic structure modification in X-ray spectroscopic studies and
highlight large-area defect manipulation and direct device patterning as
possible new fields of application for focused laboratory X-ray sources.Comment: 12 pages, 4 figure
Superconducting qubit based on twisted cuprate van der Waals heterostructures
Van-der-Waals (vdW) assembly enables the fabrication of novel Josephson
junctions utilizing an atomically sharp interface between two exfoliated and
relatively twisted (Bi2212) flakes. In a range of
twist angles around , the junction provides a regime where the
interlayer two-Cooper pair tunneling dominates the current-phase relation. Here
we propose to employ this novel junction to realize a capacitively shunted
qubit that we call flowermon. The -wave nature of the order parameter endows
the flowermon with inherent protection against charge-noise-induced relaxation
and quasiparticle-induced dissipation. This inherently protected qubit paves
the way to a new class of high-coherence hybrid superconducting quantum devices
based on unconventional superconductors.Comment: 6+5 pages, 4+4 figure
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