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Featured researches published by Toshikazu Ekino.


Japanese Journal of Applied Physics | 1987

SUPERCONDUCTING TUNNELING IN Y-Ba-Cu-O SYSTEM.

Toshikazu Ekino; Jun Akimitsu

Electron tunneling study on high-Tc superconductor Y-Ba-Cu-O system with the onset transition temperature of about 95 K has been carried out. The observed energy gap is slightly larger than that expected from the BCS theory.


Japanese Journal of Applied Physics | 1987

Electron Tunneling Study of NbSe3

Toshikazu Ekino; Jun Akimitsu

The two CDW energy gaps of NbSe3 were measured by means of the point contact tunneling technique. The peak to peak values of energy gaps at T=4.2K aretypically 2ΔH180 mV and 2ΔL73 mV from the NbSe3-Au junction, where ΔH and ΔL correspond to the higher CDW transition temperature TH=145K and lower one TL=59K, respectively. From these values, we obtained that 2ΔH/kTH=14.4 and 2ΔL/kTL=14.3, which are much larger than the DCS value.


Journal of the Physical Society of Japan | 1989

Superconducting energy gap in BaPb1-xBixO3 determined from point-contact tunneling

Toshikazu Ekino; Jun Akimitsu

Electron tunneling measurements have been performed on single crystals of BaPb 1- x Bi x O 3 with various values of x . The observed density of states in the superconducting state can well be described by the broadened BCS density of states proposed by Dynes et at. The ratio 2 Δ /k T c increases with increasing the Bi concentration of x , suggesting the increase of electron-phonon interactions, and saturates at around x ∼0.2. The values of 2 Δ /k T c in the saturated region coincide with the BCS value.


Japanese Journal of Applied Physics | 1987

Electron Tunneling Study on Superconductivity of BaPb1-xBixO3

Jun Akimitsu; Toshikazu Ekino; Kazuaki Kobayashi

The electron tunneling measurements have been performed on the single crystal of BaPb1-xBixO3 with various x around x~0.2. The observed density of states can well be described by the broadened BCS density of states proposed by Dynes et al, suggesting the gapless superconductor in BaPb1-xBixO3.


Archive | 1989

Electron Tunneling into Superconducting Bismuth-Copper Oxide Systems

Toshikazu Ekino; Jun Akimitsu

The energy gaps of the polycrystal1ine Bi-Sr-Ca-Cu-O and Bi-Sr-Cu-O superconductors have been measured by means of the point-contact tunneling technique. We find that the energy gaps at T=OK are 2Δ=76-81meV in Bi2Sr2Ca1Cu2Oy(Tc=76K), 91–100meV in Bi2Sr2Ca2Cu3Oy(Tc=105K) and 3.0–3.5meV in Bi2Sr2Cu1Oy (Tc=6.5K). Temperature variations of these energy gaps are also extracted. The ratios 2Δ/kTc are 11.6–12.4 for Bi2Sr2Ca1Cu2Oy, 10.0–11.0 for Bi2Sr2Ca2Cu3Oy, extremely larger than BCS value. 2Δ/kTc of Bi2Sr2Cu1Oy is 5.4–6.2, larger than those of the usual strong coupling superconductors. These results give the information about the difference of the pairing nature on the superconducting state between these materials which have multiple Cu02 layers or a single CuO2 layer between the SrO layers.


Physical Review B | 1989

Energy gaps in Bi-Sr-Ca-Cu-O and Bi-Sr-Cu-O systems by electron tunneling

Toshikazu Ekino; Jun Akimitsu


Physical Review B | 1989

Tunneling study on the electron-doped superconductor Nd1.85Ce0.15CuO4-y.

Toshikazu Ekino; Jun Akimitsu


青山学院大学総合研究所理工学研究センター研究叢書 | 1992

TUNNELING SPECTROSCOPY ON HIGH-T c SUPERCONDUCTORS

Toshikazu Ekino; Jun Akimitsu


青山学院大学総合研究所理工学研究センター研究叢書 | 1992

Observations of Superconducting Tunnel Conductance Structures in YBa_2Cu_3O_ Tunnel Junctions

Toshikazu Ekino; Jun Akimitsu


JJAP series | 1992

Tunneling Spectroscopy of Copper-Oxide Superconductors : III-A Superconducting Characteristics : III Oxide Superconductors, Experiments III : Superconducting State

Toshikazu Ekino; Jun Akimitsu

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Hideo Fujiki

Aoyama Gakuin University

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Hiroshi Sawa

Aoyama Gakuin University

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Yuji Matsubara

Aoyama Gakuin University

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