Terahertz Hall Measurements On Optimally Doped Single Crystal Bi-2212

The infrared Hall angle in optimally doped single crystal $\rm Bi_2 Sr_2 Ca Cu_2 O_{8+x}$ was measured from 3.05 to 21.75 meV as a continuous function of temperature from 25 to 300\,K. In the normal state, the temperature dependence of the real part of the cotangent of the infrared Hall angle obeys the same power law as dc measurements. The measured Hall frequency $\rm \omega_H$ is significantly larger than the expected value based upon ARPES data analyzed in terms of the relaxation time approximation. This discrepancy as well as the temperature dependence of $\rm Re(\cot{\theta_H})$ and $\omega_H$ is well described by a Fermi liquid theory in which current vertex corrections produced by electron-magnon scattering are included.Comment: 10 pages, 2 figure

Elucidating the role of hyperfine interactions on organic magnetoresistance using deuterated aluminium tris(8-hydroxyquinoline)

Measurements of the effect of a magnetic field on the light output and current through an organic light emitting diode made with deuterated aluminium tris(8-hydroxyquinoline) have shown that hyperfine coupling with protons is not the cause of the intrinsic organic magnetoresistance. We suggest that interactions with unpaired electrons in the device may be responsible.Comment: Submitte

Terahertz Kerr and Reflectivity Measurements on the Topological Insulator Bi2Se3

We report the first terahertz Kerr measurements on bulk crystals of the topological insulator Bi2Se3. At T=10K and fields up to 8T, the real and imaginary Kerr angle and reflectance measurements utilizing both linearly and circularly polarized incident radiation were measured at a frequency of 5.24meV. A single fluid free carrier bulk response can not describe the line-shape. Surface states with a small mass and surprisingly large associated spectral weight quantitatively fit all data. However, carrier concentration inhomogeneity has not been ruled out. A method employing a gate is shown to be promising for separating surface from bulk effects.Comment: 10 pages, 5 figure

An equatorial wind from the massive young stellar object S140 IRS 1

The discovery of the second equatorial ionized stellar wind from a massive young stellar object is reported. High resolution radio continuum maps of S140 IRS 1 reveal a highly elongated source that is perpendicular to the larger scale bipolar molecular outflow. This picture is confirmed by location of a small scale monopolar near-IR reflection nebula at the base of the blueshifted lobe. A second epoch of observations over a five year baseline show little ordered outward proper motion of clumps as would have been expected for a jet. A third epoch, taken only 50 days after the second, did show significant changes in the radio morphology. These radio properties can all be understood in the context of an equatorial wind driven by radiation pressure from the central star and inner disc acting on the gas in the surface layers of the disc as proposed by Drew et al. (1998). This equatorial wind system is briefly compared with the one in S106IR, and contrasted with other massive young stellar objects that drive ionized jets.Comment: 19 pages, 5 figures, accepted by ApJ, minor changes in light of referees repor

Magnetoresistance of YBa2Cu3O7 in the "cold spots" model

We calculate the in-plane magnetoresistance $\Delta\rho_{xx}/\rho_{xx}$ of YBa$_2$Cu$_3$O$_7$ in a magnetic field applied perpendicular to the $CuO_2$ planes for the ``cold spots'' model. In this model, the electron relaxation time $\tau_2\propto1/T^2$ at small regions on the Fermi surface near the Brillouin zone diagonals is much longer than the relaxation time $\tau_1\propto1/T$ at the rest of the Fermi surface ($T$ is temperature). In qualitative agreement with the experiment, we find that Kohler's rule is strongly violated, but the ratio $\Delta\rho_{xx}/\rho_{xx}\tan^2\theta_H$, where $\tan\theta_H$ is the Hall angle, is approximately temperature-independent. We find the ratio is about 5.5, which is of the same order of magnitude as in the experiment.Comment: RevTeX, 4 pages, 6 figures. V.2: 2 references adde

Mid-infrared Hall effect in thin-film metals: Probing the Fermi surface anisotropy in Au and Cu

A sensitive mid-infrared (MIR, 900-1100 cm-1, 112-136 meV) photo-elastic polarization modulation technique is used to measure simultaneously Faraday rotation and circular dichroism in thin metal films. These two quantities determine the complex AC Hall conductivity. This novel technique is applied to study Au and Cu thin films at temperatures down to 20 K and magnetic fields up to 8 T. The Hall frequency is consistent with band theory predictions. We report the first measurement of the MIR Hall scattering rate, which is significantly lower than that derived from Drude analysis of zero magnetic field MIR transmission measurements. This difference is qualitatively explained in terms of the anisotropy of the Fermi surface in Au and Cu.Comment: 14 pages of text, 5 figure

The Effects of Different Types of Internal Controls on Self-Control

One reason companies implement internal controls is to reduce the likelihood of unethical behavior. Yet, ego depletion theory suggests that some controls may cause reductions in employees’ self-control, which could undermine the ability of controls to reduce unethical behavior. We examine whether various types of controls impact self-control and ethical judgments. Our results show that contrary to the ego depletion hypothesis, we find no significant relation between self-control and internal controls. Furthermore, we find that controls have no effect on ethical judgments or ethical ideology. Thus, our results suggest that internal controls do not differentially impact self-control and ethical decision-making