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Nonlinear spin current generation in noncentrosymmetric spin-orbit coupled systems
Hamamoto, Keita,Ezawa, Motohiko,Kim, Kun Woo,Morimoto, Takahiro,Nagaosa, Naoto American Physical Society 2017 Physical Review B Vol.95 No.22
<P>Spin current plays a central role in spintronics. In particular, finding more efficientways to generate spin current has been an important issue and has been studied actively. For example, representative methods of spin-current generation include spin-polarized current injections from ferromagnetic metals, the spin Hall effect, and the spin battery. Here, we theoretically propose a mechanism of spin-current generation based on nonlinear phenomena. By using Boltzmann transport theory, we showthat a simple application of the electric field E induces spin current proportional to E-2 in noncentrosymmetric spin-orbit coupled systems. We demonstrate that the nonlinear spin current of the proposed mechanism is supported in the surface state of three-dimensional topological insulators and two-dimensional semiconductors with the Rashba and/or Dresselhaus interaction. In the latter case, the angular dependence of the nonlinear spin current can be manipulated by the direction of the electric field and by the ratio of the Rashba and Dresselhaus interactions. We find that the magnitude of the spin current largely exceeds those in the previous methods for a reasonable magnitude of the electric field. Furthermore, we show that application of ac electric fields (e.g., terahertz light) leads to the rectifying effect of the spin current, where dc spin current is generated. These findings will pave a route to manipulate the spin current in noncentrosymmetric crystals.</P>
The source counts of submillimetre galaxies detected at λ= 1.1 mm
Scott, K. S.,Wilson, G. W.,Aretxaga, I.,Austermann, J. E.,Chapin, E. L.,Dunlop, J. S.,Ezawa, H.,Halpern, M.,Hatsukade, B.,Hughes, D. H.,Kawabe, R.,Kim, S.,Kohno, K.,Lowenthal, J. D.,Montañ,a, A. Blackwell Publishing Ltd 2012 Monthly notices of the Royal Astronomical Society Vol.423 No.1
<P><B>ABSTRACT</B></P><P>The source counts of galaxies discovered at submillimetre and millimetre wavelengths provide important information on the evolution of infrared‐bright galaxies. We combine the data from six blank‐field surveys carried out at 1.1 mm with AzTEC, totalling 1.6 deg<SUP>2</SUP> in area with root‐mean‐square depths ranging from 0.4 to 1.7 mJy, and derive the strongest constraints to date on the 1.1 mm source counts at flux densities <I>S</I><SUB>1100</SUB>= 1–12 mJy. Using additional data from the AzTEC Cluster Environment Survey to extend the counts to <I>S</I><SUB>1100</SUB>∼ 20 mJy, we see tentative evidence for an enhancement relative to the exponential drop in the counts at <I>S</I><SUB>1100</SUB>∼ 13 mJy and a smooth connection to the bright source counts at >20 mJy measured by the South Pole Telescope; this excess may be due to strong‐lensing effects. We compare these counts to predictions from several semi‐analytical and phenomenological models and find that for most the agreement is quite good at flux densities ≳ 4 mJy; however, we find significant discrepancies (≳ 3σ) between the models and the observed 1.1‐mm counts at lower flux densities, and none of them is consistent with the observed turnover in the Euclidean‐normalized counts at <I>S</I><SUB>1100</SUB>≲ 2 mJy. Our new results therefore may require modifications to existing evolutionary models for low‐luminosity galaxies. Alternatively, the discrepancy between the measured counts at the faint end and predictions from phenomenological models could arise from limited knowledge of the spectral energy distributions of faint galaxies in the local Universe.</P>