論文 - 大橋　洋士

Unusual Proximity Effect of d-Wave Superconductivity

大橋 洋士

Journal of the Physical Society of Japan （Journal of the Physical Society of Japan）  65 （ 3 ） 823-839 - 839 1996年

研究論文（学術雑誌）, 単著, 筆頭著者, 査読有り,  ISSN  00319015

　概要を見る

A novel proximity effect, that the d-wave superconductivity induces a different symmetric order parameter in the normal metal side, is investigated for the normal metal (N)-d-wave superconductor (S) junction in the clean limit. The induced superconductivity is obtained self-consistently on the basis of the quasi-classical theory and the condition of this effect to occur is clarified. Our result shows that the deformation of the pair amplitude and the direction of the NS boundary with respect to the phase of the d-wave superconductivity are crucial in this phenomenon. A characteristic structure appearing in the local density of states due to this proximity effect is also examined comparing with the conventional case.

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Resonance State Localized around Nonmagnetic Impurity with Unitarity Scattering in Two-Dimensional d-Wave Superconductor

Onishi Y., Ohashi Y., Shingaki Y., Miyake K.

Journal of the Physical Society of Japan （Journal of the Physical Society of Japan）  65 （ 3 ） 675-678 - 678 1996年

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  00319015

　概要を見る

Effects of nonmagnetic impurities with unitarity scattering in two-dimensional d-wave superconductors are investigated by the numerical diagonalization of finite-size systems of up to 35×35 sites. It is shown that a localized state with almost zero excitation energy is formed around an impurity site if it is isolated. However, its localized state is extended in real space along the direction of the node of the d-wave gap, so that the localized states of adjacent impurities easily interfere with each other forming a kind of impurity band, i.e., resonance states around the zero energy. It is also pointed out that there exists a strong association between the resonance density of states due to impurity scattering in the unitarity limit and the so-called zero-bias anomaly of tunneling conductance.

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On the Bloch Theorem Concerning Spontaneous Electric Current

Ohashi Y., Momoi T.

Journal of the Physical Society of Japan （Journal of the Physical Society of Japan）  65 （ 10 ） 3254-3259 - 3259 1996年

研究論文（学術雑誌）, 共著, 筆頭著者, 査読有り,  ISSN  00319015

　概要を見る

We study the Bloch theorem which states absence of the spontaneous current in interacting electron systems. This theorem is shown to be still applicable to the system with the magnetic field induced by the electric current. Application to the spontaneous surface current is also examined in detail. Our result excludes the possibility of the recently proposed d-wave superconductivity having the surface flow and finite total current.

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Theoretical proposal of a method to identify the symmetry of the order parameter in high-Tc superconductivity

Ohashi Y.

Journal of the Physical Society of Japan （Journal of the Physical Society of Japan）  64 （ 3 ） 887 - 912 1995年03月

研究論文（学術雑誌）, 単著, 筆頭著者, 査読有り,  ISSN  00319015

　概要を見る

A new experimental method to judge the symmetry of the order parameter in high-Tc superconductivity is proposed. The interference of reflected holes from different directions due to the Andreev reflection causes quite different phenomena among s-,dx2-y2- and dxy-wave superconductivity. It is shown that this interference effect may be observed as a change of the conductance below Tc, which enables us to identify the symmetry of the pairing state in high-Tc superconductivity. Various cases in which the experimental setup deviates from the ideal situation are also studied and experimental condition for this method is clarified.

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Temperature Dependence of Uniform Susceptibility in High-Tc Superconductors

Ohashi Y.

Journal of the Physical Society of Japan （Journal of the Physical Society of Japan）  62 （ 10 ） 3702 - 3709 1993年

研究論文（学術雑誌）, 単著, 筆頭著者, 査読有り,  ISSN  00319015

　概要を見る

The uniform susceptibility of high-Tc cuprates is studied by focusing on its anomalous temperature dependence. Our result shows that the uniform susceptibility has a temperature dependence due to the coupling with antiferromagnetic (AF) spin fluctuations. Furthermore, the difference of the temperature dependence between the lightly doped region and the overdoped region is explained with this mechanism as related to the strength of the AF spin fluctuations. © 1993, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

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Pairing and Depairing Effects of Antiferromagnetic Spin Fluctuations in High-7c Superconductivity

Ohashi Y., Shiba H.

Journal of the Physical Society of Japan （Journal of the Physical Society of Japan）  62 （ 8 ） 2783 - 2802 1993年

研究論文（学術雑誌）, 共著, 筆頭著者, 査読有り,  ISSN  00319015

　概要を見る

The role of antiferromagnetic (AF) spin fluctuations in high-rc superconductivity is studied by including both pairing and depairing effects. Thereby the possibility and nature of superconductivity mediated by AF spin fluctuations is examined. Since both of them are based on the same electron system, the superconductivity affects also the AF spin fluctuations as a feedback effect. The present paper discusses this mutual influence to find properties which may be a key to identify experimentally the symmetry of the order parameter. © 1993, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

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Quantum Diffusion of MuonsInteracting with Superconduccting Electrons. I

M. Matsumoto and Y. Ohashi

J. Phys. Soc. Jpn. 62   2088-2097 1993年

研究論文（学術雑誌）, 共著, 最終著者, 査読有り

Quantum Diffusion of Muons Interacting with Superconducting Electrons. II

Ohashi Y., Matsumoto M.

Journal of the Physical Society of Japan （Journal of the Physical Society of Japan）  62 （ 10 ） 3532-3538 - 3538 1993年

研究論文（学術雑誌）, 共著, 筆頭著者, 査読有り,  ISSN  00319015

　概要を見る

The band motion of muons in superconductors is studied in detail. Both the damping rate and the effective mass of the muon due to the interaction with conduction electrons are examined. Then, the average hopping rate of a muon is obtained by combining these quantities. The results are compared with that obtained by the double-well model and the relation between the two is discussed. In addition, as an extention of our theory, the quantum diffusion in some unconventional superconductors is also examined. © 1993, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

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