Magnetic field effects on the density of states of orthorhombic superconductors

The quasiparticle density of states in a two-dimensional d-wave superconductor depends on the orientation of the in-plane external magnetic field H. This is because. in the region of the gap nodes, the Doppler shift due to the circulating supercurrents around a vortex depend on the direction of H. For a tetragonal system the induced pattern is four-fold symmetric and, at zero energy, the density of states exhibits minima along the node directions. But YBa_2C_3O_{6.95} is orthorhombic because of the chains and the pattern becomes two-fold symmetric with the position of the minima occuring when H is oriented along the Fermi velocity at a node on the Fermi surface. The effect of impurity scattering in the Born and unitary limit is discussed.Comment: 24 pages, 11 Figure

Synergy: A Web-Based Tool to Facilitate Dialogic Peer Feedback

Producción CientíficaThe goal of this demonstration session is to introduce Synergy, a platform to help design and implement dialogic feedback practices. Synergy is grounded in a theoretical framework of dialogic feedback, which suggests an ongoing dialogue among the peers (providing feedback) and the target student (receiving feedback). Synergy allows instructors to create multiple review sessions with specific tasks depending on the role as feedback receiver or provider. Peer review activities are organized around three phases, in accordance with theoretical framework. Using Synergy, peers in the first phase assess student work, discuss together to align their perspectives toward the quality of the work. Then, the peers create feedback tasks (to identify who gives which feedback). In the second phase, Synergy enables peers to provide the intended feedback (based on the feedback tasks) and to build dialogue with the target student. During dialogue, in collaboration with peers, Synergy allows students to identify learning actions to translate the feedback received into concrete progress. In the last phase, when students perform the planned actions, Synergy tracks student engagement and progress per each action and also allows the students to set their progress manually. Synergy is enhanced with Learning Analytics tools to support the feedback processes During the demo, we will show interactively the use case of how Synergy can help design and facilitate dialogic peer feedback.Ministerio de Ciencia, Innovación y Universidades (Project TIN2017-85179-C3-2-R and TIN2014-53199-C3-2-R)Junta de Castilla y León (project VA257P18), by the European Commission under project grant 588438-EPP-1-2017-1-EL- EPPKA2-KA

The Transit Light Curve Project. VI. Three Transits of the Exoplanet TrES-2

Of the nearby transiting exoplanets that are amenable to detailed study, TrES-2 is both the most massive and has the largest impact parameter. We present z-band photometry of three transits of TrES-2. We improve upon the estimates of the planetary, stellar, and orbital parameters, in conjunction with the spectroscopic analysis of the host star by Sozzetti and co-workers. We find the planetary radius to be 1.222 +/- 0.038 R_Jup and the stellar radius to be 1.003 +/- 0.027 R_Sun. The quoted uncertainties include the systematic error due to the uncertainty in the stellar mass (0.980 +/- 0.062 M_Sun). The timings of the transits have an accuracy of 25s and are consistent with a uniform period, thus providing a baseline for future observations with the NASA Kepler satellite, whose field of view will include TrES-2.Comment: 15 pages, including 2 figures, accepted Ap

A massive exoplanet candidate around KOI-13: Independent confirmation by ellipsoidal variations

We present an analysis of the KOI-13.01 candidate exoplanet system included in the September 2011 Kepler data release. The host star is a known and relatively bright $(m_{\rm KP} = 9.95)$ visual binary with a separation significantly smaller (0.8 arcsec) than the size of a Kepler pixel (4 arcsec per pixel). The Kepler light curve shows both primary and secondary eclipses, as well as significant out-of-eclipse light curve variations. We confirm that the transit occurs round the brighter of the two stars. We model the relative contributions from (i) thermal emission from the companion, (ii) planetary reflected light, (iii) Doppler beaming, and (iv) ellipsoidal variations in the host-star arising from the tidal distortion of the host star by its companion. Our analysis, based on the light curve alone, enables us to constrain the mass of the KOI-13.01 companion to be $M_{\rm C} = 8.3 \pm 1.25M_{\rm J}$ and thus demonstrates that the transiting companion is a planet (rather than a brown dwarf which was recently proposed by \cite{b7}). The high temperature of the host star (Spectral Type A5-7V, $T_{\rm eff} = 8511-8020$ K), combined with the proximity of its companion KOI-13.01, may make it one of the hottest exoplanets known, with a detectable thermal contribution to the light curve even in the Kepler optical passband. However, the single passband of the Kepler light curve does not enable us to unambiguously distinguish between the thermal and reflected components of the planetary emission. Infrared observations may help to break the degeneracy, while radial velocity follow-up with $\sigma \sim$ 100 m s$^{-1}$ precision should confirm the mass of the planet.Comment: 7 pages, 5 figure

Fermi-Liquid Interactions in d-Wave Superconductor

This article develops a quantitative quasiparticle model of the low-temperature properties of d-wave superconductors which incorporates both Fermi-liquid effects and band-structure effects. The Fermi-liquid interaction effects are found to be classifiable into strong and negligible renormalizaton effects, for symmetric and antisymmetric combinations of the energies of $k\uparrow$ and $-k\downarrow$ quasiparticles, respectively. A particularly important conclusion is that the leading clean-limit temperature-dependent correction to the superfluid density is not renormalized by Fermi-liquid interactions, but is subject to a Fermi velocity (or mass) renormalization effect. This leads to difficulties in accounting for the penetration depth measurements with physically acceptable parameters, and hence reopens the question of the quantitative validity of the quasiparticle picture.Comment: 4 page

Variation in Grazing Sward Chicory Content After Periods of Low Rainfall

Multispecies (MS) swards can reduce chemical nitrogen (N) fertiliser requirement due to the legume components of the sward mixtures, and have the potential to increase drought tolerance, particularly where chicory (CH, Chicorium intybus L.) is included in the sward mixture. A grazed plot experiment was established to investigate the persistency of forage herb species in MS swards under typical Irish grazing conditions. The swards contained three plant functional groups: grass, legume and herb; four sward types were established which included sward mixtures of the following species: perennial ryegrass (PRG, Lolium perenne L.) white clover (WC, Trifolium repens L.), red clover (RC, Trifolium pratense L.), CH and ribwort plantain (PL, Plantago lanceolata L.). The sward content of the various species in the sown mixtures was evaluated over three years (2020, 2021 and 2022). The summer of 2022 experienced dry weather conditions in which rainfall was well below average thus providing an opportunity to assess the drought tolerance of CH in grazed swards. The proportion of sward CH content from two late season cuts was assessed over the three years and this study reports the changes in sward CH content between years and grazing rotations. Average sward CH content was 14.7, 6.1, and 1.5% across all sward types in late summer of 2020, 2021 and 2022, respectively; average sward CH content was 13.7, 9.4 and 24.6 across all sward types in autumn of 2020, 2021 and 2022, respectively

Multiscale simulations of the electronic structure of III-nitride quantum wells with varied indium content: Connecting atomistic and continuum-based models

Carrier localization effects in III-N heterostructures are often studied in the frame of modified continuum-based models utilizing a single-band effective mass approximation. However, there exists no comparison between the results of a modified continuum model and atomistic calculations on the same underlying disordered energy landscape. We present a theoretical framework that establishes a connection between atomistic tight-binding theory and continuum-based electronic structure models, here a single-band effective mass approximation, and provide such a comparison for the electronic structure of (In,Ga)N quantum wells. In our approach, in principle, the effective masses are the only adjustable parameters since the confinement energy landscape is directly obtained from tight-binding theory. We find that the electronic structure calculated within effective mass approximation and the tight-binding model differ noticeably. However, at least in terms of energy eigenvalues, an improved agreement between the two methods can be achieved by adjusting the band offsets in the continuum model, enabling, therefore, a recipe for constructing a modified continuum model that gives a reasonable approximation of the tight-binding energies. Carrier localization characteristics for energetically low lying, strongly localized states differ, however, significantly from those obtained using the tight-binding model. For energetically higher lying, more delocalized states, good agreement may be achieved. Therefore, the atomistically motivated continuum-based single-band effective mass model established provides a good, computationally efficient alternative to fully atomistic investigations, at least at when targeting questions related to higher temperatures and carrier densities in (In,Ga)N systems

Spontaneous Flux and Magnetic Interference Patterns in 0-pi Josephson Junctions

The spontaneous flux generation and magnetic field modulation of the critical current in a 0-pi Josephson junction are calculated for different ratios of the junction length to the Josephson penetration depth, and different ratios of the 0-junction length to the pi-junction length. These calculations apply to a Pb-YBCO c-axis oriented junction with one YBCO twin boundary, as well as other experimental systems. Measurements of such a junction can provide information on the nature of the c-axis Josephson coupling and the symmetry of the order parameter in YBCO. We find spontaneous flux even for very short symmetric 0-pi junctions, but asymmetric junctions have qualitatively different behavior.Comment: 13 pages, TEX,+ 7 figures, postscrip

Warm Debris Disks Candidates in Transiting Planets Systems

We have bandmerged candidate transiting planetary systems (from the Kepler satellite) and confirmed transiting planetary systems (from the literature) with the recent Wide-field Infrared Survey Explorer (WISE) preliminary release catalog. We have found 13 stars showing infrared excesses at either 12 and/or 22 microns. Without longer wavelength observations it is not possible to conclusively determine the nature of the excesses, although we argue that they are likely due to debris disks around the stars. If confirmed, our sample ~ doubles the number of currently known warm excess disks around old main sequence stars. The ratios between the measured fluxes and the stellar photospheres are generally larger than expected for Gyr-old stars, such as these planetary hosts. Assuming temperature limits for the dust and emission from large dust particles, we derive estimates for the disk radii. These values are comparable to the planet's semi-major axis, suggesting that the planets may be stirring the planetesimals in the system.Comment: Submitted to A&A: 21 October 2011 / Accepted for publication in A&A: 27 February 201