1,721,021 research outputs found
Symmetric dynamic behaviour of a superconducting proximity array with respect to field reversal
Get PDFAs the complexity of strongly correlated systems and high temperature superconductors increases, so does also the essential complexity of defects found in these materials and the complexity of the supercurrent pathways. It can be therefore convenient to realize a solid-state system with regular supercurrent pathways and without the disguising effects of disorder in order to capture the essential characteristics of a collective dynamics. Using a square array of superconducting islands placed on a normal metal, we observe a state in which magnetic field-induced vortices are frozen in the dimples of the egg crate potential by their strong repulsion interaction. In this system a dynamic vortex Mott insulator transition has been previously observed. In this work, we will show the symmetric dynamic behaviour with respect to field reversal and we will compare it with the asymmetric behaviour observed at the dynamic vortex Mott transition.</p
Superstripes and complexity in high-temperature superconductors
No full textWhile for many years the lattice, electronic and magnetic complexity of high-temperature superconductors (HTS) has been considered responsible for hindering the search of the mechanism of HTS, now the complexity of HTS is proposed to be essential for the quantum mechanism raising the superconducting critical temperature. The complexity is shown by the lattice heterogeneous architecture: heterostructures at atomic limit; (b) electronic heterogeneity: multiple components in the normal phase; (c) superconducting heterogeneity: multiple superconducting gaps in different points of the real space and of the momentum space. The complex phase separation forms an unconventional granular superconductor in a landscape of nanoscale superconducting striped droplets, which is called the “superstripes” scenario. The interplay and competition between magnetic orbital charge and lattice fluctuations seems to be essential for the quantum mechanism that suppresses thermal decoherence effects at an optimum inhomogeneity
Far from Equilibrium Percolation, Stochastic and Shape Resonances in the Physics of Life
No full textKey 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)
Imaging Spatial Ordering of the Oxygen Chains in at the Insulator-to-Metal Transition
No full textIt is known that the mobile oxygen ions, y, in the basal plane of YBa2Cu3O6+y (0.33<y<0.67) form oxygen chains needed to create the metallic phase in the CuO2 layers. Here we visualize the spatial organization of oxygen chains in a crystal of YBa2Cu3O6+y very close to the insulator-to-superconductor transition with y=0.33 (T c =7 K). The distribution of oxygen defects chains has been obtained by performing scanning micro X-ray diffraction measurements. This experiment provides mixed real and reciprocal space information. We found a granular spatial pattern due to the oxygen chains being segregated in nanoscale puddles with ortho-II crystallographic structure embedded in an insulating matrix of disordered oxygen ions
Superconducting qubit based on twisted cuprate van der Waals heterostructures.
No full textVan-der-Waals assembly enables the fabrication of novel Josephson junctions featuring an atomically sharp interface between two exfoliated and relatively twisted
Bi
2
Sr
2
CaCu
2
O
8
+
x
(Bi2212) flakes. In a range of twist angles around 45°, the junction provides a regime where the interlayer two-Cooper pair tunneling dominates the current-phase relation. Here we propose employing this novel junction to realize a capacitively shunted qubit that we call flowermon. The
d
-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
Giant Shapiro Steps in a Superconducting Network of Nanoscale Nb Islands
Get PDFRecently, 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
Intrinsic arrested nanoscale phase separation near a topological Lifshitz transition in strongly correlated two-band metals
No full textThe arrested nanoscale phase separation in a two-band Hubbard model for strongly correlated charge carriers is shown to occur in a particular range in the vicinity of the topological Lifshitz transition, where the Fermi energy crosses the bottom of the narrow band and a new sheet of the Fermi surface related to the charge carriers of the second band comes into play. We determine the phase separation diagram of this two-band Hubbard model as a function of two variables, the charge carrier density and the energy shift between the chemical potential and the bottom of the second band. In this phase diagram, we first determine a line of quantum critical points for the Lifshitz transition and find criteria for the electronic phase separation resulting in an inhomogeneous charge distribution. Finally, we identify the critical point in the presence of a variable long-range Coulomb interaction where the scale invariance of the coexisting phases with different charge densities appears. We argue that this point is relevant for the regime of scale invariance of the nanoscale phase separation in cuprates like it was first observed in La2CuO
Two-Dimensional Nanogranularity of the Oxygen Chains in the YBa2Cu3O6.33 Superconductor
No full textThe organization of dopants in high-temperature superconductors provides complex topological geometries that control superconducting properties. This makes the study of dopants’ spatial distribution of fundamental importance. The mobile oxygen ions, y, in the CuO2 plane of YBa2Cu3O6 + y (0.33 < y < 0.67) form ordered chains which greatly affect the transport properties of the material. Here, we visualize and characterize the two-dimensional spatial organization of these oxygen chains using scanning micro X-ray diffraction measurements in transmission mode on a thin single-crystal slab with y = 0.33 (T c = 7 K) near the critical doping for the insulator-to-metal transition. We show the typical landscape of percolation made of a granular spatial pattern due the oxygen chains segregating in quasi-one-dimensional needles of ortho-II (O-II) phase embedded in an insulating matrix with low density of disordered oxygen interstitials
Phase Separation in Electron Doped Iron-Selenide K0.8Fe1.6Se2 Superconductor by Scanning X-ray Nano-Diffraction
No full textA new family of high temperature superconductors, the heavily electron doped iron-selenides, like K0.8Fe1.6Se2, has been attracting high interest since they show both 30 K superconductivity, with missing hole pockets questioning the s± pairing model, and unusually high magnetic moments. The hot debate is between coexistence versus phase separation and on the possible divergence of surface from bulk structure. Here, we provide direct evidence for a nanoscale phase separation in a single crystal of K0.8Fe1.6Se2, where a first magnetic phase, with superlattice modulation (5–√×5–√) , coexists with a second nonmagnetic phase, with a second superlattice modulation ( 2–√×2–√ ), below 520 K using transmission X-ray diffraction. The mapping of the spatial distribution of the two phases is measured by scanning X-ray nanodiffraction using a 300×300 nm2 X-ray spot. The complex spatial phase separation clarifies the coexistence of superconductivity and magnetism in the same sample
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