SU(2) approach to the pseudogap phase of high-temperature superconductors: electronic spectral functions

We use an SU(2) mean-field theory approach with input from variational wavefunctions of the t-J model to study the electronic spectra in the pseudogap phase of cuprates. In our model, the high-temperature state of underdoped cuprates is realized by classical fluctuations of the order parameter between the d-wave superconductor and the staggered-flux state. Spectral functions of the intermediate and the averaged states are computed and analyzed. Our model predicts a photoemission spectrum with an asymmetric gap structure interpolating between the superconducting gap centered at the Fermi energy and the asymmetric staggered-flux gap. This asymmetry of the gap changes sign at the point where the Fermi surface crosses the diagonal (\pi,0)-(0,\pi).Comment: 7 pages, 10 figures; estimate of applicable temperature range corrected and refs. added, ref. to ARPES paper added; minor changes to published versio

Quasiparticle spectral weights of Gutzwiller-projected high T_c superconductors

We analyze the electronic Green's functions in the superconducting ground state of the t-J model using Gutzwiller-projected wave functions, and compare them to the conventional BCS form. Some of the properties of the BCS state are preserved by the projection: the total spectral weight is continuous around the quasiparticle node and approximately constant along the Fermi surface. On the other hand, the overall spectral weight is reduced by the projection with a momentum-dependent renormalization, and the projection produces electron-hole asymmetry in renormalization of the electron and hole spectral weights. The latter asymmetry leads to the bending of the effective Fermi surface which we define as the locus of equal electron and hole spectral weight.Comment: 6 pages, 5 figures; x-labels on Figs. 1 and 2 corrected, footnote on particle number corrected, references adde

Carotenoids and Antioxidant Nutrients following Burn Injury a

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72213/1/j.1749-6632.1993.tb26193.x.pd

Haydeeite: a spin-1/2 kagome ferromagnet

The mineral haydeeite, alpha-MgCu3(OD)6Cl2, is a S=1/2 kagome ferromagnet that displays long-range magnetic order below TC=4.2 K with a strongly reduced moment. Our inelastic neutron scattering data show clear spin-wave excitations that are well described by a Heisenberg Hamiltonian with ferromagnetic nearest-neighbor exchange J1=-38 K and antiferromagnetic exchange Jd=+11 K across the hexagons of the kagome lattice. These values place haydeeite very close to the quantum phase transition between ferromagnetic order and non-coplanar twelve-sublattice cuboc2 antiferromagnetic order. Diffuse dynamic short-range ferromagnetic correlations observed above TC persist well into the ferromagnetically ordered phase with a behavior distinct from critical scattering

An experimental investigation of microresistor laser printing with gold nanoparticle-laden inks

This paper presents an experimental investigation of the novel thermal manufacturing process of printing and laser curing of nanoparticle-laden inks that can produce functional microstructures such as electronic microresistors and interconnections for semiconductors and other devices. Of specific interest are the complex and interweaved transport phenomena involved, focusing on the absorption and diffusion processes of irradiated laser energy influencing solvent vaporization, the nanoparticle curing process, the substrate, and the final quality of the produced resistor. Parametric studies of the thermal process together with extensive microscopy analysis of the topography and resistivity measurements piece together a better understanding of the underlying physics and aid the development of the technolog

Positive Cross Correlations in a Normal-Conducting Fermionic Beam Splitter

We investigate a beam splitter experiment implemented in a normal conducting fermionic electron gas in the quantum Hall regime. The cross-correlations between the current fluctuations in the two exit leads of the three terminal device are found to be negative, zero or even positive depending on the scattering mechanism within the device. Reversal of the cross-correlations sign occurs due to interaction between different edge-states and does not reflect the statistics of the fermionic particles which `antibunch'.Comment: 4 pages, 4 figure

Toxic Substances

This part of the CBP Synthesis Report summarizes and integrates the research findings and reconnnendations of 13 projects of the Chesapeake Bay Toxic Substances Program performed between July 1978 and October 1981. The following sections describe research on potentially toxic substances, or toxicants, in water-sediments and selected biota. The subjects considered include a brief review of metals, their sources, distribution and behavior, and then a review of sources and distribution of organic chemicals. Finally, information concerning the significance of toxicants in the- Bay and their pattern of enrichment is provided. Most information synthesized in this report can be traced to its origin in scientific project reports listed in Appendix A.https://scholarworks.wm.edu/vimsbooks/1097/thumbnail.jp

The energy and dynamics of trapped radiative feedback with stellar winds

In this paper, we explore the significant, non-linear impact that stellar winds have on H II regions. We perform a parameter study using three-dimensional radiative magnetohydrodynamic simulations of wind and ultraviolet radiation feedback from a 35 M⊙ star formed self-consistently in a turbulent, self-gravitating cloud, similar to the Orion Nebula (M42) and its main ionizing source θ1 Ori C. Stellar winds suppress early radiative feedback by trapping ionizing radiation in the shell around the wind bubble. Rapid breakouts of warm photoionized gas (‘champagne flows’) still occur if the star forms close to the edge of the cloud. The impact of wind bubbles can be enhanced if we detect and remove numerical overcooling caused by shocks crossing grid cells. However, the majority of the energy in the wind bubble is still lost to turbulent mixing between the wind bubble and the gas around it. These results begin to converge if the spatial resolution at the wind bubble interface is increased by refining the grid on pressure gradients. Wind bubbles form a thin chimney close to the star, which then expands outwards as an extended plume once the wind bubble breaks out of the dense core the star formed in, allowing them to expand faster than a spherical wind bubble. We also find wind bubbles mixing completely with the photoionized gas when the H II region breaks out of the cloud as a champagne flow, a process we term ‘hot champagne’

The effect of magnetic fields on properties of the circumgalactic medium

We study the effect of magnetic fields on a simulated galaxy and its surrounding gaseous halo, or circumgalactic medium (CGM), within cosmological 'zoom-in' simulations of a Milky Way-mass galaxy as part of the Simulating the Universe with Refined Galaxy Environments (SURGE) project. We use three different galaxy formation models, each with and without magnetic fields, and include additional spatial refinement in the CGM to improve its resolution. The central galaxy's star formation rate and stellar mass are not strongly affected by the presence of magnetic fields, but the galaxy is more disc dominated and its central black hole is more massive when B > 0. The physical properties of the CGM change significantly. With magnetic fields, the circumgalactic gas flows are slower, the atomic hydrogen-dominated extended discs around the galaxy are more massive and the densities in the inner CGM are therefore higher, the temperatures in the outer CGM are higher, and the pressure in the halo is higher and smoother. The total gas fraction and metal mass fraction in the halo are also higher when magnetic fields are included, because less gas escapes the halo. Additionally, we find that the CGM properties depend on azimuthal angle and that magnetic fields reduce the scatter in radial velocity, whilst enhancing the scatter in metallicity at fixed azimuthal angle. The metals are thus less well-mixed throughout the halo, resulting in more metal-poor halo gas. These results together show that magnetic fields in the CGM change the flow of gas in galaxy haloes, making it more difficult for metal-rich outflows to mix with the metal-poor CGM and to escape the halo, and therefore should be included in simulations of galaxy formation