物質創成科学研究科 / Graduate School of Materials Science
http://hdl.handle.net/10061/6645
Wed, 06 Dec 2017 23:40:32 GMT2017-12-06T23:40:32ZMagnetic Properties of Fibonacci-Modulated Fe-Au Multilayer Metamaterials
http://hdl.handle.net/10061/12182
Magnetic Properties of Fibonacci-Modulated Fe-Au Multilayer Metamaterials
Suwa, Tomomi; Tomita, Satoshi; Hosoito, Nobuyoshi; Yanagi, Hisao
Herein we experimentally study magnetic multilayer metamaterials with broken translational symmetry. Epitaxially-grown iron-gold (Fe-Au) multilayers modulated using Fibonacci sequence—referred to as magnetic inverse Fibonacci-modulated multilayers (IFMs)—are prepared using ultra-high-vacuum vapor deposition. Experimental results of in-situ reflection high-energy electron diffraction, magnetization curves, and ferromagnetic resonance demonstrate that the epitaxially-grown Fe-Au IFMs have quasi-isotropic magnetization, in contrast to the in-plane magnetization easy axis in the periodic multilayers.
Fri, 20 Oct 2017 00:00:00 GMThttp://hdl.handle.net/10061/121822017-10-20T00:00:00ZMicrowave analog of Stern-Gerlach effects using nonuniform chiral metamaterials
http://hdl.handle.net/10061/12137
Microwave analog of Stern-Gerlach effects using nonuniform chiral metamaterials
Tomita, Satoshi; Sawada, Kei; Nagai, Shotaro; Sanada, Atsushi; Hisamoto, Nobuyuki; Ueda, Tetsuya
This study observes microwave beam splitting dependent on circular polarizations through nonuniform chiral metamaterials. Nonuniform chiral metamaterials with a gradation in refractive index are constructed using chiral meta-atoms that exhibit optical activities at microwave frequencies. Microwave scattering far-field patterns by the nonuniform chiral metamaterials demonstrate a deflection of microwaves, which transmit in a direction perpendicular to the refractive index gradient. Furthermore, circularly polarized microwaves with opposite “spins of light” go their separate ways in the nonuniform chiral metamaterials. This phenomenon is an optical analog of the Stern-Gerlach effects for electrons.
Fri, 13 Oct 2017 00:00:00 GMThttp://hdl.handle.net/10061/121372017-10-13T00:00:00ZTwo-Photon Absorption by Impurity Scattering and Amplitude Mode in Conventional Superconductors
http://hdl.handle.net/10061/12122
Two-Photon Absorption by Impurity Scattering and Amplitude Mode in Conventional Superconductors
Jujo, Takanobu
We theoretically investigate the two-photon absorption spectrum of conventional s-wave superconductors. The calculation is carried out in the local limit at absolute zero. The direct excitation of quasiparticles is excluded under the condition that the frequency of the external field is lower than twice the magnitude of the superconducting gap. We calculate vertex corrections with the conserving approximation, and show that the amplitude mode is independent of the impurity scattering in the local limit. Because of this property, a diverging absorption edge appears in the dirty limit. We propose this behavior as a probe of the amplitude mode.
Fri, 23 Oct 2015 00:00:00 GMThttp://hdl.handle.net/10061/121222015-10-23T00:00:00ZRelaxation Dynamics of Photoinduced Changes in the Superfluid Weight of High-Tc Superconductors
http://hdl.handle.net/10061/12118
Relaxation Dynamics of Photoinduced Changes in the Superfluid Weight of High-Tc Superconductors
Jujo, Takanobu
In the transient state of d -wave superconductors, we investigate the temporal variation of photoinduced changes in the superfluid weight. We derive the formula that relates the nonlinear response function to the nonequilibrium distribution function. The latter quantity is obtained by solving the kinetic equation with the electron-electron and the electron-phonon interaction included. By numerical calculations, a nonexponential decay is found at low temperatures in contrast to the usual exponential decay at high temperatures. The nonexponential decay originates from the nonmonotonous temporal variation of the nonequilibrium distribution function at low energies. The main physical process that causes this behavior is not the recombination of quasiparticles as previous phenomenological studies suggested, but the absorption of phonons.
Mon, 27 Dec 2010 00:00:00 GMThttp://hdl.handle.net/10061/121182010-12-27T00:00:00Z