6,157 research outputs found

    Terahertz Hall Measurements On Optimally Doped Single Crystal Bi-2212

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    The infrared Hall angle in optimally doped single crystal Bi2Sr2CaCu2O8+x\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 ωH\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 Re(cotθH)\rm Re(\cot{\theta_H}) and ωH\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)

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    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

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    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

    Temperature dependent optical studies of Ti1x_{1-x}Cox_xO2_2

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    We present the results of Raman and photoluminescence (PL) studies on epitaxial anatase phase Ti1x_{1-x}Cox_xO2_2 films for xx = 0-0.07, grown by pulsed laser deposition. The low doped system (xx=0.01 and 0.02) shows a Curie temperature of ~700 K in the as-grown state. The Raman spectra from the doped and undoped films confirm their anatase phase. The photoluminescence spectrum is characterized by a broad emission from self-trapped excitons (STE) at 2.3 eV at temperatures below 120 K. This peak is characteristic of the anatase-phase TiO2_2 and shows a small blueshift with increasing doping concentration. In addition to the emission from STE, the Co-doped samples show two emission lines at 2.77 eV and 2.94 eV that are absent in the undoped film indicative of a spin-flip energy.Comment: 8 pages, 4 figure

    The Shackles of Peer Review: Unveiling the Flaws in the Ivory Tower

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    This essay delves into the ethical dilemmas encountered within the academic peer review process and investigates the prevailing deficiencies in this system. It highlights how established scholars often adhere to mainstream theories not out of genuine belief, but to safeguard their own reputations. This practice perpetuates intellectual conformity, fuels confirmation bias, and stifles dissenting voices. Furthermore, as the number of incorrect papers published by influential scientists increases, it inadvertently encourages more researchers to follow suit, tacitly endorsing incorrect viewpoints. By examining historical instances of suppressed ideas later proven valuable, this essay calls for a reevaluation of academia's commitment to genuine innovation and progress which is usually achieved by applications of fundamental principles in from textbooks.Comment: 10 pages, 0 figure

    Near-Infrared Spectroscopy of McNeil's Nebula Object

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    We present 0.8-5.2 micron spectroscopy of the compact source at the base of a variable nebula (McNeil's Nebula Object) in the Lynds 1630 dark cloud that went into outburst in late 2003. The spectrum of this object reveals an extremely red continuum, CO bands at 2.3-2.5 microns in emission, a deep 3.0 micron ice absorption feature, and a solid state CO absorption feature at 4.7 microns. In addition, emission lines of H, Ca II, Mg I, and Na I are present. The Paschen lines exhibit P Cygni profiles, as do two lines of He I, although the emission features are very weak in the latter. The Brackett lines, however, are seen to be purely in emission. The P Cygni profiles clearly indicate that mass outflow is occurring in a wind with a velocity of ~400 km/s. The H line ratios do not yield consistent estimates of the reddening, nor do they agree with the extinction estimated from the ice feature (A_V ~ 11). We propose that these lines are optically thick and are produced in a dense, ionized wind. The near-infrared spectrum does not appear similar to any known FUor or EXor object. However, all evidence suggests that McNeil's Nebula Object is a heavily-embedded low-mass Class I protostar, surrounded by a disk, whose brightening is due to a recent accretion event.Comment: 11 pages, 2 ps figures, accepted for publication in ApJ Letter

    Hypoxic Induction of Anoxia Tolerance in Roots of Adh1 Null Zea mays L

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