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Superconductivity evolves as functions of pressure or doping fromcharge-ordered phases in a variety of strongly correlated systems, suggestingthat there may be universal characteristics associated with the competitionbetween superconductivity and charge order in these materials. We present aninelastic light (Raman) scattering study of the structural changes that precedethe pressure-tuned charge-density-wave (CDW) to superconductor transition inone such system, ZrTe3. In certain phonon bands, we observe dramatic linewidthreductions that accompany CDW formation, indicating that these phonons couplestrongly to the electronic degrees of freedom associated with the CDW. The samephonon bands, which represent internal vibrations of ZrTe3 prismatic chains,are suppressed at pressures above ~10 kbar, indicating a loss of long-rangeorder within the chains, specifically amongst intrachain Zr-Te bonds. Theseresults suggest a distinct structural mechanism for the observedpressure-induced suppression of CDW formation and provide insights into theorigin of pressure-induced superconductivity in ZrTe3.

The grounding line is a key element of coastal outlet glaciers, acting on their dynamics. Accurately knowing its position is fundamental for both modelling the glacier dynamics and establishing a benchmark for later change detection. Here we map the grounding line of the Astrolabe Glacier in East Antarctica (66°41' S, 140°05' E), using both hydrostatic and tidal methods. The first method is based on new surface and ice thickness data from which the line of buoyant floatation is found. The second method uses kinematic GPS measurements of the tidal response of the ice surface. By detecting the transitions where the ice starts to move vertically in response to the tidal forcing we determine control points for the grounding line position along GPS profiles. Employing a two-dimensional elastic plate model, we compute the rigid short-term behaviour of the ice plate and estimate the correction required to compare the kinematic GPS control points with the previously determined line of floatation. These two approaches show consistency and lead us to propose a grounding line for the Astrolabe Glacier that significantly deviates from the lines obtained so far from satellite imagery. © Author(s) 2014. CC Attribution 3.0 License.

The ferrimagnetic spinels MnB2O4 (B=Mn,V) exhibit a similar series of closely spaced magnetic and structural phase transitions at low temperatures, reflecting both magnetic frustration and a strong coupling between the spin and lattice degrees of freedom. Careful studies of excitations in MnB2O4 (B=Mn,V), and the evolution of these excitations with temperature, are important for obtaining a microscopic description of the role that magnetic excitations and spin-lattice coupling play in the low-temperature phase transitions of these materials. We report an inelastic light (Raman) scattering study of the temperature and magnetic-field dependences of one- and two-magnon excitations in MnV2O4 and Mn3O4. We observe a pair of q=0 one-magnon modes at 74 and 81 cm-1 in MnV2O4, which is in contrast with the single 80-cm-1 q=0 magnon that has been reported for MnV2O4 based on previous neutron-scattering measurements and spin-wave calculations. Additionally, we find that the two-magnon energy of MnV2O4 decreases ("softens") with decreasing temperature below TN, which we attribute to strong coupling between magnetic and vibrational excitations near the zone boundary. © 2014 American Physical Society.

The ferrimagnetic spinels MnB2O4 (B=Mn,V) exhibit a similar series of closely spaced magnetic and structural phase transitions at low temperatures, reflecting both magnetic frustration and a strong coupling between the spin and lattice degrees of freedom. Careful studies of excitations in MnB2O4 (B=Mn,V), and the evolution of these excitations with temperature, are important for obtaining a microscopic description of the role that magnetic excitations and spin-lattice coupling play in the low-temperature phase transitions of these materials. We report an inelastic light (Raman) scattering study of the temperature and magnetic-field dependences of one- and two-magnon excitations in MnV2O4 and Mn3O4. We observe a pair of q=0 one-magnon modes at 74 and 81 cm-1 in MnV2O4, which is in contrast with the single 80-cm-1 q=0 magnon that has been reported for MnV2O4 based on previous neutron-scattering measurements and spin-wave calculations. Additionally, we find that the two-magnon energy of MnV2O4 decreases ("softens") with decreasing temperature below TN, which we attribute to strong coupling between magnetic and vibrational excitations near the zone boundary. © 2014 American Physical Society.

We present the Warm Ice Sounding Explorer (WISE), a low-frequency (2.5 MHz) radar for the sounding of temperate ice. WISE deployment in southern Alaska in 2008 and 2012 provides comprehensive measurements of glacier thickness, reveals deep valleys beneath glaciers and the full extent of zones grounded below sea level. The east branch of Columbia Glacier is deeper that its main branch and remains below sea level 20 km farther inland. Ice is 1000 m deep on Tazlina Glacier. On Bering glacier, two sills separate three deep bed depressions (>1200 m) that coincide with the dynamic balance lines during surges. The piedmont lobe of Malaspina Glacier and the lower reaches of Hubbard Glacier are entirely grounded below sea level 40 and 10 km, respectively, from their termini. Knowledge of ice thickness in these regions helps better understand their glacier dynamics, mass balance, and impact on sea level. Key Points Low frequency radar sounding works extremely well in Alaska Ice is much thicker than suggested by limited surveys Data reveals full extent of areas grounded below sea level ©2013. American Geophysical Union. All Rights Reserved.

The Cassini Titan Radar Mapper obtained Synthetic Aperture Radar images of Titan's surface during four fly-bys during the mission's first year. These images show that Titan's surface is very complex geologically, showing evidence of major planetary geologic processes, including cryovolcanism. This paper discusses the variety of cryovolcanic features identified from SAR images, their possible origin, and their geologic context. The features which we identify as cryovolcanic in origin include a large (180 km diameter) volcanic construct (dome or shield), several extensive flows, and three calderas which appear to be the source of flows. The composition of the cryomagma on Titan is still unknown, but constraints on rheological properties can be estimated using flow thickness. Rheological properties of one flow were estimated and appear inconsistent with ammonia-water slurries, and possibly more consistent with ammonia-water-methanol slurries. The extent of cryovolcanism on Titan is still not known, as only a small fraction of the surface has been imaged at sufficient resolution. Energetic considerations suggest that cryovolcanism may have been a dominant process in the resurfacing of Titan. Keywords: Titan; Volcanism; Satellites of Saturn

Author(s): E. R. Stofan (corresponding author) [1, 2]; C. Elachi [3]; J. I. Lunine [4]; R. D. Lorenz [5]; B. Stiles [3]; K. L. Mitchell [3]; S. Ostro [3]; L. [...]

The first two swaths collected by Cassini's Titan Radar Mapper were obtained in October of 2004 (Ta) and February of 2005 (T3). The Ta swath provides evidence for cryovolcanic processes, the possible occurrence of fluvial channels and lakes, and some tectonic activity. The T3 swath has extensive areas of dunes and two large impact craters. We interpret the brightness variations in much of the swaths to result from roughness variations caused by fracturing and erosion of Titan's icy surface, with additional contributions from a combination of volume scattering and compositional variations. Despite the small amount of Titan mapped to date, the significant differences between the terrains of the two swaths suggest that Titan is geologically complex. The overall scarcity of impact craters provides evidence that the surface imaged to date is relatively young, with resurfacing by cryovolcanism, fluvial erosion, aeolian erosion, and likely atmospheric deposition of materials. Future radar swaths will help to further define the nature of and extent to which internal and external processes have shaped Titan's surface. Keywords: Titan; Geological processes; Saturn, satellites; Satellites, surfaces

Author(s): C. Elachi [1]; S. Wall (corresponding author) [1]; M. Janssen [1]; E. Stofan [2]; R. Lopes [1]; R. Kirk [3]; R. Lorenz [4]; J. Lunine [4, 5]; F. Paganelli [...]

The Cassini Titan Radar Mapper imaged about 1% of Titan's surface at a resolution of ~0.5 kilometer, and larger areas of the globe in lower resolution modes. The images reveal a complex surface, with areas of low relief and a variety of geologic features suggestive of dome-like volcanic constructs, flows, and sinuous channels. The surface appears to be young, with few impact craters. Scattering and dielectric properties are consistent with porous ice or organics. Dark patches in the radar images show high brightness temperatures and high emissivity and are consistent with frozen hydrocarbons., Saturn's largest satellite, Titan, is the only moon and one of only four solid bodies in the solar system to host a thick atmosphere, uniquely distinguished by nitrogen and methane [...]

High-temperature superconducting Josephson junctions were grown in a ramp-edge superconductor-normal metal-superconductor (SNS) configuration using highly stable normal-metal barrier materials such as the cation-modified and corrosion-resistant compound (pryGd(sub 0.6-y))Ca0.4Ba1.6La0.4Cu3O7. The fabricated junctions were observed to exhibit well-defined RSJ-like current and voltage characteristics at liquid-nitrogen temperature.It was also noted that the junction performance is primarily regulated by the N-layer.

Transport measurements done at various applied magnetic fields were used in the critical-current measurements for YBa2Cu3O7-delta, Gd0.6Ca0.4Ba1.6LaO.4Cu3O7-delta and TX-GBCO/YBCO bilayer films which were prepared by pulsed laser deposition and patterned as microbridges. For TX-GBCO/YBCO bilayers, the highest Jc at 75 K in 5 Tesla was observed showing a 40% increase in Jc over YBCO under the same conditions.

Pulsed laser deposition on various single crystl substrates was used to fabricate epitaxial (rare earth)Ba2Cu3O7 films, RE123, with RE = Y, Er and Sm. Each material's deposition was optimized for T(sub c). An increase in ionic sized of the rare-earth element was observed in increased T(sub c) in RE123 films. In addition, the vortex pinning anisotropy was affected by the rare-earth element as shown by the study of field- and angle-dependent J(sub c).

Superconducting quantum interference devices (SQUIDs) were proposed for magnetic microscopy applications. The SQUID microscropes were developed using high- and low-temperature superconductor systems. Further studies on SQUID techniques are needed to reduce magnetic noise and vibrations and to allow a simple, compact low-temperature SQUID to operate close to room-temperature.

Twinned thin-film YBa2Cu3O7-delta-Ag-PbIn SQUIDs were analyzed using a 4.2 K scanning SQUID microscope. The microscope also measured the phase of the SQUIDs' order parameter for 13 different tunneling angles. Results show that the SQUIDs' order parameter is time-reversal symmetric to 5% in the a-b plane. The results also cancel certain time-reversal breaking order parameters .

The time and spatial symmetry of the superconducting order parameter in YBCO is determined using a scanning superconducting quantum interference device microscope to perform a time-reversal invariance test. Results indicate a time-reversal invariant dx2-y2 symmetric component in YBCO's order parameter. Moreover, the amplitude of any imaginary isotropic s-wave symmetric component and any real s-wave component to be less than 6% and 89%, respectively.

The feasibility of using superconducting quantum interference devices (SQUIDs) resolution magnetic resonance microscopy measurements was evaluated. Experiments were conducted wherein a SQUID is used to monitor the position of a sample target under different magnetic field levels. Results indicate that the proposed SQUID magnetic flux microscope is very useful for obtaining absolute magnetic field measurements with high accuracy.

Recent comparative studies of quasiparticle injection from colossal magnetoresistance (CMR) materials and normal metals into high transition temperature superconductors (HTS) have led several investigators to conclude that spin-polarized injection from CMR electrodes is far more efficient than ordinary injection in suppressing superconductivity. On the other hand, some ordinary quasiparticle injection experiments have shown greater suppression of superconductivity than was claimed in any of the published spin-injection experiments. Careful analysis and numerical simulations lead us to argue that all spin-injection experiments to date have been hampered by inadequate control samples and that the reported results can be explained by ordinary (unpolarized) quasiparticle injection or simple current summation. We conclude that there is no conclusive evidence that spin-polarized injection into HTS behaves differently from ordinary quasiparticle injection and we discuss criteria for future experiments that could differentiate between the two types of injection. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The Northern and Southern Patagonian Icefields are the largest ice masses in the Southern Hemisphere outside Antarctica, but their ice volume and bed topography are poorly known. Here, we combine airborne gravity data collected in 2012 and 2016, with radar data from the Warm Ice Experiment Sounder and Centro de Estudios Científicos's to map bed elevation and ice thickness in great detail. We perform a 3‐D inversion of the gravity data constrained by radar‐derived thickness and fjord bathymetry to infer bed elevation at 500‐m spacing, with a precision of about 60 m. We detect deep glacial valleys with ice thickness exceeding 1,400 m and sectors below sea level on the western branch of Glaciar Pio XI, Occidental, between San Rafael and Colonia, and near Fitz Roy. We calculate an ice volume of 4,756 ± 923 km3 for Northern Patagonia Icefield and Southern Patagonia Icefield, or 40 times the volume of glaciers in the European Alps. Plain Language Summary: Traditional techniques of radar depth sounding fail to resolve thick, temperate ice masses due to poor penetration of the radar signals into snow and ice and extensive scattering due to water content. We combine sparse airborne radar sounding and bathymetry data with novel high‐resolution, high‐precision airborne gravity data to infer the bed topography of the Patagonia Icefields of South America. The results reveal the full range of deep ice thickness on the plateau, portions of the icefields grounded below sea level, and the total volume content of the Patagonia Icefields. The results are critical to constrain the details of the past, present, and future evolution of this glaciated region in a warmer climate. Key Points: Comprehensive ice thickness and bed elevation measurements are conducted on the Northern and Southern Patagonian Icefields of South AmericaIce thickness in excess of 1,400 m is observed over selected regions of the plateauA multisensor approach solves the problem of mapping the thickness of temperate ice masses [ABSTRACT FROM AUTHOR]