Static semifluxons in a long Josephson junction with π-discontinuity points

We investigate analytically a long Josephson junction with several $\pi$-discontinuity points characterized by a jump of $\pi$ in the phase difference of the junction. The system is described by a perturbed-combined sine-Gordon equation. Via phase-portrait analysis, it is shown how the existence of static semifluxons localized around the discontinuity points is influenced by the applied bias current. In junctions with more than one corner, there is a minimum-facet-length for semifluxons to be spontaneously generated. A stability analysis is used to obtain the minimum-facet-length for multicorner junctions

Unexpected observation of spatially separated Kondo scattering and ferromagnetism in Ta alloyed anatase TiO2 thin films

We report the observation of spatially separated Kondo scattering and ferromagnetism in anatase Ta 0.06 Ti 0.94 O 2 thin films as a function of thickness (10\u2013200 nm). The Kondo behavior observed in thicker films is suppressed on decreasing thickness and vanishes below ~25 nm. In 200 nm film, transport data could be fitted to a renormalization group theory for Kondo scattering though the carrier density in this system is lower by two orders of magnitude, the magnetic entity concentration is larger by a similar magnitude and there is strong electronic correlation compared to a conventional system such as Cu with magnetic impurities. However, ferromagnetism is observed at all thicknesses with magnetic moment per unit thickness decreasing beyond 10 nm film thickness. The simultaneous presence of Kondo and ferromagnetism is explained by the spatial variation of defects from the interface to surface which results in a dominantly ferromagnetic region closer to substrate-film interface while the Kondo scattering is dominant near the surface and decreasing towards the interface. This material system enables us to study the effect of neighboring presence of two competing magnetic phenomena and the possibility for tuning them

Effect of Nb and Ta substitution on donor electron transport and ultrafast carrier dynamics in anatase TiO2 thin films

Ta and Nb substituted TiO 2 are important transparent conducting oxides that have potential for applications in photovoltaics, photocatalysis, and water splitting/CO2 sequestration. In addition to donating electrons, what are the e\ufb00ects of Nb and Ta substitution? Here we observe strong experimental evidence that Ta and Nb substitution induces large and small polarons in anatase TiO2 epitaxial thin films. The degenerate donor electrons (from both Nb and Ta) show a high temperature T ^3 dependence on electrical resistivity, which confirms the presence of large polarons, along with room temperature metallic transport. This is further confirmed by the enhancement in the electron e\ufb00ective mass, which was estimated from thermopower measurements. Femtosecond transient absorption (fs-TA) reveals the life time of the Ti-t 2g and e g levels and the separation of these levels are consistent with the X-ray absorption spectroscopy (XAS) measurement. In addition, fs-TA reveals the presence of small polarons with a life time substantially 41 ns, which arises from defect levels and is a consequence of Ta and Nb substitution. X-ray photoelectron spectroscopy (XPS) provides evidence of Ti 3+ , which may be identified as the defects responsible for the small polarons. These long-lived small polarons may provide a way to minimize recombination dynamics in TiO 2 -based electrodes for photo-excited devices