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Effects of Mechanical Rotation and Vibration on Spin Currents
Mamoru Matsuo,Jun’ichi Ieda,Sadamichi Maekawa,Eiji Saitoh 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.10
We discuss theoretically the generation of spin currents in both rotationally and linearly accelerated systems. The spin-orbit interaction modified by inertial effects is derived from the low energy limit of the generally covariant Dirac equation. It is shown that the spin-orbit interaction is responsible for the generation of spin currents by mechanical rotation and vibration. We also study effects of impurity scattering on the mechanically induced spin current, and calculate the spin accumulation by solving the spin diffusion equation with the spin-source term originating from the inertial effects.
Yoon, Yo-Seop,Lee, Won-Yong,Park, No-Won,Kim, Gil-Sung,Ramos, Rafael,Takashi, Kikkawa,Saitoh, Eiji,Koo, Sang-Mo,Park, Jin-Seong,Lee, Sang-Kwon The Royal Society of Chemistry 2019 Journal of materials chemistry. C, Materials for o Vol.7 No.6
<P>Superlattice thin films, which are used in thermoelectric (TE) devices for small-scale solid-state cooling and for generating electrical power, have recently been attracting attention due to their low dimensionality, low thermal conductivity, and enhanced power factor. Considering the measurement techniques for characterizing TE properties, very limited information, including cross-plane Seebeck coefficients of superlattice films, has been reported. This information is required for the assessment of the interface between the films and to understand phonon scattering in superlattice films. In this report, thermally stable cross-plane thermoelectric Seebeck coefficients of Al2O3/ZnO (AO/ZnO) superlattice films are presented, at temperature differences (Δ<I>T</I>) ranging from 2 to 12 K. Longitudinal (in-plane) thermal diffusion in the Cu/AO/ZnO/Cu samples, which occurred during the measurements due to the size differences among the samples located between a micro-Peltier and aluminum nitride cooling plate, was investigated. The cross-plane Seebeck coefficients of 3- and 6-cycled AO/ZnO superlattice films were determined to be ∼9.4 ± 0.4 and ∼30.6 ± 0.7 μV K<SUP>−1</SUP>, respectively, showing stable values in the evaluated Δ<I>T</I> range. Two distinct phenomena, in-plane thermal diffusion and the effect of the environment, were identified in cross-plane Seebeck measurements as dominant factors controlling the temperature coefficient of AO/ZnO superlattice films. In addition, a new TE parameter, the Seebeck temperature coefficient, was proposed for superlattice films.</P>
Park, No-Won,Kang, Dae Yun,Lee, Won-Yong,Yoon, Yo-Seop,Kim, Gil-Sung,Saitoh, Eiji,Kim, Tae Geun,Lee, Sang-Kwon American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.26
<P>We investigate the intrinsic thermoelectric (TE) properties of the metal-diffused aluminum oxide (AO) layer in metal/AO/metal structures, where the metallic conducting filaments (CFs) were locally formed in the structures via an electrical breakdown (EBD) process as shown by resistive switching memory devices, by directly measuring cross-plane Seebeck coefficients on the CF-containing insulating AO layers. The results showed that the Seebeck coefficients of the CF-containing AO layer in metal/AO/metal structures were influenced by the generation of the metallic CFs, which is due to the diffusion of the metal into the insulating AO layers when exposed to a temperature gradient in the direction of the cross plane of the sample. In addition, the increase in the Seebeck coefficients of the CF-containing AO layer when the number of EBD-processed patterns was increased is satisfactorily explained by the low-energy carrier (i.e., minority carriers) filtering through the metal-oxide interfacial barriers in the metal/AO/metal structures.</P> [FIG OMISSION]</BR>
Park, No-Won,Lee, Won-Yong,Yoon, Yo-Seop,Ahn, Jay-Young,Lee, Jung-Hoon,Kim, Gil-Sung,Kim, Tae Geun,Choi, Chel-Jong,Park, Jin-Seong,Saitoh, Eiji,Lee, Sang-Kwon American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.51
<P>There is a recent interest in semiconducting superlattice films because their low dimensionality can increase the thermal power and phonon scattering at the interface in superlattice films. However, experimental studies in all cross-plane thermoelectric (TE) properties, including thermal conductivity, Seebeck coefficient, and electrical conductivity, have not been performed from these semiconducting superlattice films because of substantial difficulties in the direct measurement of the Seebeck coefficient and electrical conductivity. Unlike the conventional measurement method, we present a technique using a structure of sandwiched superlattice films between two embedded heaters as the heating source, and electrodes with two Cu plates, which directly enables the investigation of the Seebeck coefficient and electrical conductivity across the Al<SUB>2</SUB>O<SUB>3</SUB>/ZnO superlattice films, prepared by the atomic layer deposition method. Used in combination with the promising cross-plane four-point probe 3-ω method, our measurements and analysis demonstrate all cross-plane TE properties of Al<SUB>2</SUB>O<SUB>3</SUB>/ZnO superlattice films in the temperature range of 80 to 500 K. Our experimental methodology and the obtained results represent a significant advancement in the understanding of phonons and electrical transports in nanostructured materials, especially in semiconducting superlattice films in various temperature ranges.</P> [FIG OMISSION]</BR>