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Hayashi, Nobuhiko; Iniotakis, C.*; Machida, Masahiko; Sigrist, M.*
Physica C, 468(7-10), p.844 - 847, 2008/04
Times Cited Count：13 Percentile：50.61(Physics, Applied)We study the Josephson effect between a conventional 
-wave superconductor and a non-centrosymmetric superconductor with Rashba spin-orbit coupling. Rashba spin-orbit coupling affects the Josephson pair tunneling in a characteristic way. The Josephson coupling can be decomposed into two parts, a "spin-singlet-like" and a "spin-triplet-like" component. The latter component can lead to shift of the Josephson phase by 
relative to the former coupling. This has important implications on interference effects and may explain some recent experimental results for the Al/CePt
Si junction.
Machida, Masahiko; Kano, Takuma*; Yamada, Susumu; Okumura, Masahiko; Imamura, Toshiyuki*; Koyama, Tomio*
Physica C, 468(7-10), p.689 - 694, 2008/04
Times Cited Count：18 Percentile：59.82(Physics, Applied)no abstracts in English
Nakajima, Susumu*; Kato, Masaru*; Koyama, Tomio*; Machida, Masahiko; Ishida, Takekazu*; Nori, F.*
Physica C, 468(7-10), p.769 - 772, 2008/04
Times Cited Count：4 Percentile：21.82(Physics, Applied)A d-dot is a superconducting composite structure of d- and s-wave superconductors, which shows spontaneous half-quantized magnetic fluxes. We developed numerical method to analyze the time development of these spontaneous magnetic fluxes, based on the twocomponents Ginzburg-Landau equation. The d-dot can be used as an element of quantum dot cellular automata logic gates. We show a simulation, which demonstrates the transfer of information between two d-dot's.
Matsumoto, Hideki*; Koyama, Tomio*; Machida, Masahiko
Physica C, 468(7-10), p.654 - 659, 2008/04
Times Cited Count：17 Percentile：58.23(Physics, Applied)The terahertz wave emission from the intrinsic Josephson junctions is one of recent topics in high 
superconductors. We investigate, by numerical simulation, properties of the electromagnetic waves excited by a constant bias current in the single- and multi-Josephson junctions. Nonlinear equations of phase-differences are solved numerically by treating the effects of the outside electromagnetic fields as dynamical boundary conditions. It is shown that the emitted power of the electromagnetic wave can become large near certain retrapping points of the I-V characteristics. An instability of the inside phase oscillation is related to large amplitude of the oscillatory waves. In the single- (or homogeneous mutli-) Josephson junctions, electromagnetic oscillations can occur either in a form of standing waves (shorter junctions) or by formation of vortex-antivortex pairs (longer junctions). How these two effects affects the behavior of electromagnetic waves in the intrinsic Josephson junctions is discussed.
Ishida, Takekazu*; Matsushima, Yoshiaki*; Shimizu, Makoto*; Hayashi, Masahiko*; Ebisawa, Hiromichi*; Sato, Osamu*; Kato, Masaru*; Koyama, Tomio*; Machida, Masahiko; Sato, Kazuo*; et al.
Physica C, 468(7-10), p.576 - 580, 2008/04
Times Cited Count：3 Percentile：17.12(Physics, Applied)The extended Little-Parks effect of superconducting network is known as a periodic variation as a function of magnetic field. Superconducting Pb honeycomb networks of matching field 0.106 G and triangular microhole lattice of Pb of matching field 0.425 G have been fabricated by the combination of electron-beam lithography and a lift-off process of evaporated Pb films. The application of magnetic field corresponds to the vortex filling into superconducting networks. We measured the magnetization of the networks systematically by using a SQUID magnetometer. We found that flux jump appears rather periodically as a function of magnetic field. Flux jumps may be induced by a periodic decrease of the critical current density of the network. To the authors' knowledge, this is for the first time to observe the regular flux jumps due to the critical current modification coming from the extended Little-Parks effect of the superconducting networks.
