Relaxation of Spin Polarized 3^3He in Mixtures of 3^3He and 4^4He Below the 4^4He Lambda Point

We report the first study of the depolarization behavior of spin polarized 3He in a mixture of 3He-4He at a temperature below the 4He Lambda point in a deuterated TetraPhenyl Butadiene-doped deuterated PolyStyrene (dTPB-dPS) coated acrylic cell. In our experiment the measured 3He relaxation time is due to the convolution of the 3He longitudinal relaxation time, T1, and the diffusion time constant of 3He in superfluid 4He since depolarization takes place on the walls. We have obtained a 3He relaxation time ~3000 seconds at a temperature around 1.9K. We have shown that it's possible to achieve values of wall depolarization probability on the order of (1-2)x10^-7 for polarized 3He in the superfluid 4He from a dTPB-dPS coated acrylic surface.Comment: The Model used to interpret the data has been change

Self-consistent Coulomb picture of an electron-electron bilayer system

In this work we implement the self-consistent Thomas-Fermi approach and a local conductivity model to an electron-electron bilayer system. The presence of an incompressible strip, originating from screening calculations at the top (or bottom) layer is considered as a source of an external potential fluctuation to the bottom (or top) layer. This essentially yields modifications to both screening properties and the magneto-transport quantities. The effect of the temperature, inter-layer distance and density mismatch on the density and the potential fluctuations are investigated. It is observed that the existence of the incompressible strips plays an important role simply due to their poor screening properties on both screening and the magneto-resistance (MR) properties. Here we also report and interpret the observed MR Hysteresis within our model.Comment: 12 pages, 12 figures, submitted to PR

Structure and magnetism of MnAu nanoclusters

Equiatomic MnAu clusters with average sizes of 4 and 10 nm are produced by inert-gas condensation. As-produced clusters are used to form both dense cluster films and films with clusters embedded in a W matrix with a cluster volume fraction of 25%. Both structure and magnetism are size-dependent. Structural analysis of the 10 nm clusters indicate a distorted tetragonal body-centered cubic structure with lattice parameters a=0.315 and c=0.329 nm. The 4 nm clusters have a partially ordered tetragonal L10 structure with lattice parameters a=0.410 nm and c=0.395 nm. Magnetic properties of the clusters show evidence at low temperatures of mixed ferromagnetic and antiferromagnetic interactions and ordering as well as paramagnetic spins. Saturation moments are as large as 0.54 μB per average Mn atom. The results are compared with earlier theoretical calculations on bulk MnAu

Enhanced Direct CP Violation in B±→ρ0π±B^{\pm} \to \rho^{0} \pi^{\pm}

We study direct CP violation in the hadronic decay $B^{\pm} \to \rho^{0}\pi^{\pm}$, including the effect of $\rho - \omega$ mixing. We find that the CP violating asymmetry is strongly dependent on the CKM matrix elements, especially the Wolfenstein parameter $\eta$. For fixed $N_{c}$ (the effective parameter associated with factorization), the CP violating asymmetry, $a$, has a maximum of order $30$ when the invariant mass of the $\pi^{+}\pi^{-}$ pair is in the vicinity of the $\omega$ resonance. The sensitivity of the asymmetry, $a$, to $N_{c}$ is small. Moreover, if $N_{c}$ is constrained using the latest experimental branching ratios from the CLEO collaboration, we find that the sign of $\sin \delta$ is always positive. Thus, a measurement of direct CP violation in $B^{\pm} \to \rho^{0}\pi^{\pm}$ would remove the mod$(\pi)$ ambiguity in ${\rm arg}[ - \frac{V_{td}V_{tb}^{\star}}{V_{ud}V_{ub}^{\star}}]$.Comment: 37 pages, 7 figure

Expansion of the Vortex Cores in YBa2Cu3O6.95 at Low Magnetic Fields

Muon spin rotation spectroscopy has been used to measure the effective size of the vortex cores in optimally doped YBa2Cu3O6.95 as a function of temperature and magnetic field deep in the superconducting state. While the core size at H=2T is close to 20 angstroms and consistent with that measured by STM at 6T, we find a striking increase in the core size at lower magnetic fields, where it approaches an extraordinarily large value of about 100 angstroms. This suggests that the average value of the superconducting coherence length in cuprate superconductors may be larger than previously thought at low magnetic fields.Comment: 9 pages, 4 figures, 1 text fil

Uncovering the Global Life Cycles of the Rare Earth Elements

The rare earth elements (REE) are a group of fifteen elements with unique properties that make them indispensable for a wide variety of emerging, critical technologies. Knowledge of the life cycles of REE remains sparse, despite the current heightened interest in their future availability. Mining is heavily concentrated in China, whose monopoly position and potential restriction of exports render primary supplies vulnerable to short and long-term disruption. To provide an improved perspective we derived the first quantitative life cycles (for the year 2007) for ten REE: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and yttrium (Y). Of these REE, Ce and Nd in-use stocks are highest; the in-use stocks of most REE show significant accumulation in modern society. Industrial scrap recycling occurs only from magnet manufacture. We believe there is no post-customer recycling of any of these elements

Quasiparticle structure in antiferromagnetism around the vortex and nuclear magnetic relaxation time

On the basis of the Bogoliubov-de Gennes theory for the two-dimensional extended Hubbard model, the vortex structure in d-wave superconductors is investigated including the contribution of the induced incommensurate antiferromagnetism around the vortex core. As the on-site repulsive interaction $U$ increases, the spatial structure of charge and spin changes from the antiferromagnetic state with checkerboard modulation to that with the stripe modulation. By the effect of the induced antiferromagnetic moment, the zero-energy density of states is suppressed, and the vortex core radius increases. We also study the effect of the local density of states (LDOS) change on the site-dependent nuclear relaxation rate $T_1^{-1}({\bf r})$. These results are compared with a variety of experiments performed on high $T_c$ cuprates.Comment: 10pages, 8 figure

Measuring β\beta in B→D∗+D∗−KsB \to D^{*+}D^{*-}K_s Decays

We consider the possibility of measuring both $\sin (2 \beta)$ and $\cos (2 \beta)$ in the KM unitarity triangle using the process $B^0 \to D^{*+}D^{*-}K_s$. This decay mode has a higher branching fraction (O(1%)) than the mode $B^0 \to D^{*+}D^{*-}$. We use the factorization assumption and heavy hadron chiral perturbation theory to estimate the branching fraction and polarization. The time dependent rate for $B^0(t) \to D^{*+} D^{*-} K_s$ can be used to measure $\sin (2 \beta)$ and $\cos(2 \beta)$ . Furthermore, examination of the $D^{*+} K_s$ mass spectrum may be the best way to experimentally find the broad $1^+$ p-wave $D_s$ meson.Comment: Revtex, 28 pages, 7 figures, title changed, introduction expanded, added references, details of calculations moved to the appendi

Trace and antitrace maps for aperiodic sequences, their extensions and applications

We study aperiodic systems based on substitution rules by means of a transfer-matrix approach. In addition to the well-known trace map, we investigate the so-called `antitrace' map, which is the corresponding map for the difference of the off-diagonal elements of the 2x2 transfer matrix. The antitrace maps are obtained for various binary, ternary and quaternary aperiodic sequences, such as the Fibonacci, Thue-Morse, period-doubling, Rudin-Shapiro sequences, and certain generalizations. For arbitrary substitution rules, we show that not only trace maps, but also antitrace maps exist. The dimension of the our antitrace map is r(r+1)/2, where r denotes the number of basic letters in the aperiodic sequence. Analogous maps for specific matrix elements of the transfer matrix can also be constructed, but the maps for the off-diagonal elements and for the difference of the diagonal elements coincide with the antitrace map. Thus, from the trace and antitrace map, we can determine any physical quantity related to the global transfer matrix of the system. As examples, we employ these dynamical maps to compute the transmission coefficients for optical multilayers, harmonic chains, and electronic systems.Comment: 13 pages, REVTeX, now also includes applications to electronic systems, some references adde