Solid 4He may acquire superfluid characteristics due to the frustration of the solid phase at grain boundaries. Here, introducing a negative-U generalized Hubbard model and a coarse-grained semiclassical pseudospin model, we show that an analogous effect occurs in systems with competition among charge-density-waves (CDW) and superconductivity in the presence of disorder, as cuprate or dichalcogenide superconductors. The CDW breaks apart in domains with topologically protected filamentary superconductivity at the interfaces. Our transport measurements, carried out in underdoped La2−x
Sr
x
CuO4, with the magnetic field acting as a control parameter, are shown to be in excellent agreement with our theoretical prediction. Assuming superconductivity and CDW phases have similar energies, at intermediate temperatures, the magnetic field drives the system from a fluctuating superconductor to a CDW as expected in the clean limit. Lowering the temperature, the expected clean quantum critical point is avoided and a filamentary phase appears, analogous to ‘glassy’ supersolid phenomena in 4He. The transition line ends at a second quantum critical point at high-fields. Within our scenario, the filamentary superconducting phase is parasitic with CDW and bulk superconducting phases playing the role of primary competing order parameters.
-We report enhanced superconductivity in bilayer thin films consisting of superconducting La1.6−xNd0.4SrxCuO4 with 0.06 ≤ x < 0.20 and metallic but non-superconducting La1.55Sr0.45CuO4. These bilayers show a maximum increase in superconducting transition temperature (Tc) of more than 200 % for x = 0.06 while no change in Tc is observed for the bilayers with x ≥ 0.20. The analysis of the critical current and kinetic inductance data suggests 2-3 unit cells thick interfacial layer electronically perturbed to have a higher Tc. A simple charge transfer model with cation intermixing explains the observed Tc in bilayers. Still the unusually large thickness of interfacial superconducting layers can not be explained in terms of this model. We believe the stripe relaxation as well as the proximity effect also influence the superconductivity of the interface.Introduction. -A number of recent experiments and theories have provided a new insight of remarkably different electronic properties of the interfaces between two correlated electron systems as compared to those of the parent compounds in their bulk form [1]. One of the unusual realizations of these effects is the superconductivity (SC) seen at the interface of a certain class of oxides [2][3][4][5][6] . Similar T c enhancement in electron doped cuprates has been observed for bilayers and multilayers consisting of underdoped (UD) and overdoped (OD) components [7]. The material and process factors responsible for the enhanced T c have been identified as the substrate induced strain due to lattice mismatch [8], the presence of excess oxygen [9], and the inter-diffusion of ions at the interface [3]. From a theoret-
The evolution of magnetic domain structure in epitaxial La 0.625 Ca 0.375 MnO 3 films on (001) NdGaO 3 is monitored as a function of temperature and magnetic field using Magnetic Force Microscopy. We see two distinct regions of magnetic orientational order; one in-plane displaying contrast-less image and the other tilted away from the film plane forming a distinct stripe pattern.A strong domain splitting is observed at the boundary of two regions, which is resilient to reorientation with temperature and magnetic field. We propose a model magnetic free energy functional to explain the mechanism of domain splitting seen in manganite films.
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