Silica-supported titania powders with 50, 36, 13 and 4 wt% of TiO2 (TiO2-50/SiO2, TiO2-36/SiO2, TiO2-13/SiO2 and TiO2-4/SiO2) were prepared by hydrolysis of TiCl4 in the presence of silica, followed by calcination at 500 degrees C. The formation of Ti-O-Si linkages was confirmed by diffuse reflectance infrared Fourier transform spectroscopy. Atomic force microscopy indicated the presence of titania crystals larger than 15 nm. All supported materials exhibited a blue-shift of the TiO2 absorption edge, which was attributed to an electronic semiconductor support interaction. Bandgap energies of TiO2-50/SiO2, TiO2-36/SiO2, TiO2-13/SiO2 and TiO(2)4/SiO2 were measured to be 3.28, 3.36, 3.40 and 3.42 eV, respectively, as compared to 3.15 eV for unsupported TiO2. From these values, and from the quasi-Fermi level of electrons, a high anodic shift of both the valence and the conduction band was estimated. X-ray photoelectron spectroscopy (XPS) measurements of oxygen 1s- and titanium 2p-binding energies confirmed the anodic shift of the band edges.

Transport, magnetic and optical investigations on EuRbFe 4 As 4 single crystals evidence that the ferromagnetic ordering of the Eu 2+ magnetic moments at T N = 15 K, below the superconducting transition (Tc = 36 K), affects superconductivity in a weak but intriguing way. Upon cooling below T N , the zero resistance state is preserved and the superconductivity is affected by the in-plane ferromagnetism mainly at domain boundaries; a perfect diamagnetism is recovered at low temperatures. The infrared conductivity is strongly suppressed in the far-infrared region below Tc, associated with the opening of a complete superconducting gap at 2∆ = 10 meV. A gap smaller than the weak coupling limit suggests the strong orbital effects or, within a multiband superconductivity scenario, the existence of a larger yet unrevealed gap.New members of the iron-pnictide family, the so-called 1144-compounds, attract interest recently because the alternating layers of alkaline A and alkaline-earth B cations produce two different kinds of As sites [1][2][3][4]. These materials can be viewed as the intergrowth of A-122 and B-122 iron-pnictides and they are naturally hole doped. The parent compounds are superconducting with transition temperatures T c around 35 K, higher than most of the 122materials; no spin-density-wave order has been observed. Among all possible candidates, Eu-based 1144-systems are even more intriguing, since the Eu-sublattice orders ferromagnetically below a critical temperature T N ≈ 15 K [5,6], similar to the 122-counterpart EuFe 2 As 2 [7-11]. Ferromagnetic order deep inside the superconducting state is very rare, in general [12,13]; hence the "ferromagnetic superconductor" EuRbFe 4 As 4 might pave the way towards realization of a "superconducting ferromagnet" [14-16]. However, the exact nature of the Eu magnetic order and its effect on superconductivity is unresolved [5, 6] because single crystals have been synthesized only recently.In this Letter we focus on the interplay between superconductivity and ferromagnetism in EuRbFe 4 As 4 single crystals. We report comprehensive investigations comprising transport, magnetic and optical measurements combined with microscopic studies of the vortex dynamics. The infrared spectra show a clear gap opening around 80 cm −1 below T c = 36 K that is slightly reduced compared to the value expected from the BCS theory. We relate this small value to the multiband character of superconductivity as well as to the depairing (orbital) effects of super-currents screening the ferromagnetic domains. A surprisingly weak effect on the superconducting condensate has been observed upon magnetic ordering indicating a rather weak interaction between Eu-and Fe-sublattices.Single crystals of EuRbFe 4 As 4 are obtained according to Ref. [4,5,17,18]; they exhibit shiny ab-faces of approximately 1 mm in size. The structure of the compound is presented in Fig. 1(a). The crystals are characterized by x-ray, electrical transport, and magnetic susceptibility measurements. In Fig. 1(a) we plot the dc ...

Josephson vortices play an essential role in superconducting quantum electronics devices. Often seen as purely conceptual topological objects, 2 π -phase singularities, their observation and manipulation are challenging. Here we show that in Superconductor—Normal metal—Superconductor lateral junctions Josephson vortices have a peculiar magnetic fingerprint that we reveal in Magnetic Force Microscopy (MFM) experiments. Based on this discovery, we demonstrate the possibility of the Josephson vortex generation and manipulation by the magnetic tip of a MFM, thus paving a way for the remote inspection and control of individual nano-components of superconducting quantum circuits.

This article discusses different approaches to build up supramolecular nanoarchitectures on surfaces, which were simultaneously investigated by scanning tunneling microscopy (STM) on the single-molecule level. Following this general road map, first, the hydrogen-bonding guided self-assembly of two different, structural-equivalent molecular building blocks, azobenzene dicarboxylic acid and stilbene dicarboxylic acid, was studied. Secondly, the coordination chemistry of the same building blocks, now acting as ligands in metal coordination reactions, towards co-sublimed Fe atoms was studied under near surface-conditions. Extended two-dimensional tetragonal network formation with unusual Fe2L(4/2)-dimers at the crossing points was observed on copper surfaces. Complementary to the first two experiments, a two-step approach based on the solution-based self-assembly of square-like tetranuclear complexes of the M4L4-type with subsequent deposition on graphite surfaces was investigated. One- and two-dimensional arrangements as well as single molecules of the M4L4-complexes could be observed. Moreover, the local electronic properties of a single M4L4-complexes could be probed with submolecular resolution by means of scanning tunnelling spectroscopy (STS).