Inverse proximity effect at superconductor-ferromagnet interfaces: Evidence for induced triplet pairing in the superconductor

Considerable evidence for proximity-induced triplet superconductivity on the ferromagnetic side of a superconductor-ferromagnet (S-F) interface now exists; however, the corresponding effect on the superconductor side has hardly been addressed. We have performed scanning tunneling spectroscopy measurements on NbN superconducting thin films proximity coupled to the half-metallic ferromagnet La2/3Ca1/3MnO3 (LCMO) as a function of magnetic field. We have found that at zero and low applied magnetic fields the tunneling spectra on NbN typically show an anomalous gap structure with suppressed coherence peaks and, in some cases, a zero-bias conductance peak. As the field increases to the magnetic saturation of LCMO where the magnetization is homogeneous, the spectra become more BCS-like and the critical temperature of the NbN increases, implying a reduced proximity effect. Our results therefore suggest that triplet-pairing correlations are also induced in the S side of an S-F bilayer.Comment: 12 pages, 3 figure

Reducing Stress and Preventing Anxiety in African American Adolescents: A Culturally-Grounded Approach

Evidenced-based and culturally adapted stress-reduction interventions for urban African American adolescents who are at risk for anxiety and other problems related to stress are needed. This study presents intervention components and preliminary outcome findings of a culturally adapted stress-reduction intervention for urban African American adolescents. Preliminary findings support the efficacy of the intervention to reduce anxiety and enhance general cognitive competencies, such as coping strategies, self-efficacy, and positive thinking, among participants, in comparison to controls. Clinical implications of the stress-reduction intervention for the prevention of psychopathology, particularly among African American adolescents, are discussed

Colloquium: Spin-orbit effects in superconducting hybrid structures

Spin-orbit coupling (SOC) describes the interaction between an electron's motion and its spin, and is ubiquitous in condensed matter systems. The interplay of SOC with superconductivity has attracted significant interest over the past decade and understanding has substantially progressed, both experimentally and theoretically. Even with well-understood materials, conventional $s$-wave superconducting hybrid structures with SOC provide a platform for realizing exotic phenomena and counterparts in the normal state. Understanding the emergent phenomena in such systems is an important aim in condensed matter physics. One such area relates to the generation and interplay of spin-polarized spin-triplet Cooper pairs in superconducting structures with magnetic interfaces. It is established that certain forms of magnetic inhomogeneity at an $s$-wave superconductor interface with a ferromagnet can transform spin-singlet Cooper pairs into a spin-polarized spin-triplet Cooper pairs, enabling transformative concepts for cryogenic computing. Recently, theory and experiments have demonstrated singlet-to-triplet pair conversion via SOC in $s$-wave superconducting structures with or without magnetic layers. Moreover, the spin-dependent properties of quasiparticles and their non-equilibrium behavior also change in the presence of SOC. These breakthroughs create the potential for energy-efficient control of static and dynamic spin phenomena in superconducting structures and devices. This article reviews progress in superconducting spintronics with a focus on the coupling of superconductivity and SOC in hybrid structures and devices, and outlines directions that are critical for future device development and fundamental understanding.Comment: 34 pages, 14 figure

A Review of Electronic Transport in Superconducting Sr 2 RuO 4 Junctions

We review electronic transport in superconducting junctions with Sr2RuO4. Transport measurements provide evidence for chiral domain walls and, therefore, chiral superconductivity in superconducting Sr2RuO4, but so far, the symmetry of the underlying superconducting state remains inconclusive. Further studies involving density of states measurements and spin-polarised transport in local/non-local Sr2RuO4 junctions with magnetic materials could lead to fundamental discoveries and a better understanding of the superconducting state

Imaging of Ultraluminous Infrared Galaxies in the Near-UV

We present the first ground-based U' (3410 angstroms) images of Ultraluminous Infrared Galaxies (ULIGs). Strong U' emission (median total M_U' = -20.8) is seen in all systems and in some cases the extended tidal features (both the smooth stellar distribution and compact star-forming features) contribute up to 60-80% of the total flux. The star-forming regions in both samples are found to have ages based on spectral synthesis models in the range 10-100 Myrs, and most differences in color between them can be attributed to the effects of dust reddening. Additionally, it is found that star-formation in compact knots in the tidal tails is most prominent in those ULIGs which have double nuclei, suggesting that the star-formation rate in the tails peaks prior to the actual coalescence of the galaxy nuclei and diminishes quickly thereafter. Similar to results at other wavelengths, the observed star formation at U' can only account for a small fraction of the known bolometric luminosity of the ULIGs. Azimuthally averaged radial light profiles at U' are characterized by a sersic law with index n=2, which is intermediate between an exponential disk and an r^(-1/4) law and closely resembles the latter at large radii. The implications of this near-ultraviolet imaging for optical/near-infrared observations of high redshift counterparts of ULIGs are discussed.Comment: 30 pages, 4 tables, and 9 figures, 2 of which are JPEGs. To appear in the August, 2000 edition of the Astronomical Journa

Multiple Andreev reflections in two-dimensional Josephson junctions with broken time-reversal symmetry

Andreev bound states (ABS) occur in Josephson junctions when the total phase of the Andreev and normal reflections is a multiple of $2\pi$. In ballistic junctions with an applied voltage bias, a quasi-particle undergoes multiple Andreev reflections before entering the leads, resulting in peaks in the current-voltage $I(V)$ curve. Here we present a general model for Josephson junctions with spin-active interlayers i.e., magnetic or topological materials with broken time-reversal symmetry. We investigate how ABS change the peak positions and shape of $I(V)$, which becomes asymmetric for a single incident angle. We show how the angle-resolved $I(V)$ curve becomes a spectroscopic tool for the chirality and degeneracy of ABS.Comment: 5 pages, 3 figure