d_{x^2-y^2} Symmetry and the Pairing Mechanism

An important question is if the gap in the high temperature cuprates has d_{x^2-y^2} symmetry, what does that tell us about the underlying interaction responsible for pairing. Here we explore this by determining how three different types of electron-phonon interactions affect the d_{x^2-y^2} pairing found within an RPA treatment of the 2D Hubbard model. These results imply that interactions which become more positive as the momentum transfer increases favor d_{x^2-y^2} pairing in a nearly half-filled band.Comment: 9 pages and 2 eps figs, uses revtex with epsf, in press, PR

Bulk experimental evidence of half-metallic ferromagnetism in doped manganites

We report precise measurements and quantitative data analysis on the low-temperature resistivity of several ferromagnetic manganite films. We clearly show that there exists a T^{4.5} term in low-temperature resistivity, and that this term is in quantitative agreement with the quantum theory of two-magnon scattering for half metallic ferromagnets. Our present results provide the first bulk experimental evidence of half-metallic ferromagnetism in doped manganites.Comment: 4 pages, 4 figure

Structural and Electronic Properties of a Carbon Nanotorus: Effects of Delocalized Vs Localized Deformations

The bending of a carbon nanotube is studied by considering the structural evolution of a carbon nanotorus from elastic deformation to the onset of the kinks and eventually to the collapse of the walls of the nanotorus. The changes in the electronic properties due to {\it non-local} deformation are contrasted with those due to {\it local} deformation to bring out the subtle issue underlying the reason why there is only a relatively small reduction in the electrical conductance in the former case even at large bending angles while there is a dramatic reduction in the conductance in the latter case at relatively small bending angles.Comment: 10 pages, 6 figure

Theoretical STM signatures and transport properties of native defects in carbon nanotubes

Article on theoretical STM signatures and transport properties of native defects in carbon nanotubes

National identity predicts public health support during a global pandemic

Changing collective behaviour and supporting non-pharmaceutical interventions is an important component in mitigating virus transmission during a pandemic. In a large international collaboration (Study 1, N = 49,968 across 67 countries), we investigated self-reported factors associated with public health behaviours (e.g., spatial distancing and stricter hygiene) and endorsed public policy interventions (e.g., closing bars and restaurants) during the early stage of the COVID-19 pandemic (April-May 2020). Respondents who reported identifying more strongly with their nation consistently reported greater engagement in public health behaviours and support for public health policies. Results were similar for representative and non-representative national samples. Study 2 (N = 42 countries) conceptually replicated the central finding using aggregate indices of national identity (obtained using the World Values Survey) and a measure of actual behaviour change during the pandemic (obtained from Google mobility reports). Higher levels of national identification prior to the pandemic predicted lower mobility during the early stage of the pandemic (r = −0.40). We discuss the potential implications of links between national identity, leadership, and public health for managing COVID-19 and future pandemics.publishedVersio

The influence of anharmonic phonons on the isotope effect in high- Tc oxides

Anharmonic phonons are examined to study the unusual isotope effect exponents for the high-{Tc} oxides. Within a simple model of anharmonicity, the mass dependences of the electron-phonon coupling constant {lambda} and the phonon frequency determine the isotope effect exponent {alpha} as a function of coupling strength. A model in which the outer wells of a multiple-well potential deepen as the orthorhombic/low temperature tetragonal phase transition in La{sub 2-x}M{sub x}CuO{sub 4} is approached is consistent with some experimentally observed variations in {Tc} and {alpha}. 10 refs

Theoretical modeling of edge-controlled growth kinetics and structural engineering of 2D-MoSe2

WOS:000681068200004We introduce the first reactive force field (ReaxFF) for Mo/Se/H interactions, which enables large-scale molecular dynamics simulations of the synthesis, processing, and characterization of 2D-MoSe2 and whose parameters are trained primarily on first-principles energetics data including both periodic and non-periodic calculations. This new potential elucidates the structural transition from metallic to semiconducting phases, the energetics of various defects, and the Se-vacancy migration barrier. A theoretical model developed based on this potential and the Wulff construction also describes an observed morphology evolution of 2D-MoSe2 domains during growth. Since controllable edge-mediated growth kinetics of 2D-MoSe2 are of great interest to the 2D community, we believe that this new ReaxFF potential trained against the edge formation energies of MoSe2 nanoribbons with different Se coverages will be a powerful complementary tool to experimental studies by simulating the edge-growth kinetics of 2D-MoSe2 at high speed and low cost