Doped SrTiO3 thin films are of significant scientific interest for their superconducting, ferroelectric, and thermoelectric properties. Air-exposed doped suffer from surface carrier depletion that makes it difficult to obtain thin, conducting films, especially at low doping densities temperatures. Here, we show (10 nm) EuTiO3 capping layers can prevent allow heterostructures with as 10 nm. We a...

Since the discovery of the novel iron-based superconductors, both theoretical and experimental studies have been performed intensively. Because iron-based superconductors have a smaller anisotropy than high-Tc cuprates and a high superconducting transition temperature, there have been a lot of researchers working on the film fabrication of iron-based superconductors and their application. Accor...

We have developed a method for the growth of epitaxial high T, superconducting thin films with roughness smaller than one unit cell using conventional magnetron sputtering. In this method the substrate is positioned above one edge of the target (off axis) to avoid resputtering, and oscillated back and forth between the two symmetrical edges of the target to improve film thickness homogeneity. F...

We present a quantitative comparison of the magnetization measured by spin-polarized neutron reflectivity (SPNR) and DC magnetometry on a 1370 Å -thick Nb superconducting film. As a function of magnetic field applied in the film plane, SPNR exhibits reversible behavior whereas the DC magnetization shows substantial hysteresis. The difference between these measurements is attributed to a rotatio...

We have directly measured quasiparticle number fluctuations in a thin film superconducting Al resonator in thermal equilibrium. The spectrum of these fluctuations provides a measure of both the density and the lifetime of the quasiparticles. We observe that the quasiparticle density decreases exponentially with decreasing temperature, as theoretically predicted, but saturates below 160 mK to 25...

At the charge neutral point, graphene exhibits a very unusual high-resistance metallic state and a transition to a complete insulating phase in a strong magnetic field. We propose that the current carriers in this state are the charged vortices of the XY valley-pseudospin order parameter, a situation which is dual to a conventional thin superconducting film. We study energetics and the stabilit...

A hybrid system, consisting of an array of Fe nanodots covered by a superconducting Al thin film, exhibits very unusual magnetotransport, including a giant hysteretic magnetoresistance with different reversible or irreversible regimes related to the magnetic state of the array. These effects originate from the magnetic fields produced by magnetic nanodots in the "magnetic vortex state." This is...

We describe the first direct measurement of the pair interaction potential for magnetic flux lines in a Type-II superconductor. Our approach relies on quantitative analysis of Lorentz microscope images of vortices creeping through a superconducting thin film. Time-resolved vortex distributions imaged in this way reflect both the vortices’ mutual interaction and also the influence of random pinn...

We describe current-voltage measurements on superconducting Nb/lnGaAs junction field-effect transistors which reveal a crossover from tunneling-dominated to Andreev scattering-dominated transport at the superconductor-semiconductor contacts as Schottky barrier thickness decreases with increasing interfacial dopant concentration. These measurements are the first demonstration of such a crossover...

We recently reported on a Transition Edge Sensor (TES) composite bolometer for Fourier Transform spectroscopy which was designed, built and characterized. The design is based on a superconducting thermistor with SQUID readout, SiN membrane technology and a thin film metal mesh absorber which is optimized for the spectral range from 0.1 THz to 3 THz. A noise equivalent power (NEP) of 3.8×10-13 W...