著者

Sekimoto S. Watanabe C. Minami H. Yamamoto T. Kashiwagi T. Klemm Richard A. Kadowaki K.

出版者

American Institute of Physics

雑誌

Applied physics letters (ISSN:00036951)

巻号頁・発行日

vol.103, no.18, pp.182601, 2013-10

被引用文献数

67 5

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Using a modified mesa structure of high-Tc superconducting Bi2Sr2CaCu2O8+δ with a thin underlaying base superconductor (∼3 μm), the effective working temperature of the continuous and monochromatic terahertz emitter is extended up to 70 K, and the maximum power of ∼30 μW at 0.44 THz is achieved at the relatively high temperature of T b = 55 K in a low bias current retrapping region. The diverging behavior of the intensity occurring at 55 K in the low current regime without hot spot formation may provide us an important clue for the stronger THz radiation from intrinsic Josephson junction devices.

著者

Mirković J. Savel’ev S. E. Sugahara E. Kadowaki K.

出版者

American Physical Society

雑誌

Physical review B (ISSN:01631829)

巻号頁・発行日

vol.66, no.13, pp.132505, 2002-10

被引用文献数

13 12

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The vortex-liquid and vortex-solid phases in single crystals of Bi2Sr2CaCu2O8+δ placed in tilted magnetic fields are studied by in-plane resistivity measurements using the Corbino geometry to avoid spurious surface-barrier effects. It was found that the anisotropy of the vortex-solid phase increases with temperature and exhibits a maximum at T≈0.97Tc. In contrast, the anisotropy of the vortex-liquid phase rises monotonically across the whole measured temperature range. The observed behavior is discussed in the context of dimensional crossover and thermal fluctuations of vortices in the strongly layered system.

著者

Kawano-Furukawa H. Yoshizawa H. Takeya H. Kadowaki K.

出版者

American Physical Society

雑誌

Physical review B (ISSN:01631829)

巻号頁・発行日

vol.66, no.21, pp.212503, 2002-12

被引用文献数

6 7

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An anomalous phonon peak that appears only in the superconducting state has been reported for nonmagnetic intermetallic superconductor RNi211B2C (R=Y, Lu). In the present paper, we shall demonstrate that another rare-earth borocarbide ErNi211B2C seems to show similar phonon anomalies. A spectral weight transfer from the above-lying TA phonon mode to the aforementioned peak was rather small, but it is consistent with the theoretical prediction for the system with smaller 2Δ/Eph ratio. Combining the present results with those observed in the other borocarbide systems, we suggest that such a phonon anomaly might be a common phenomenon for superconductors with a strong nesting feature of the Fermi surface.

著者

Machida Y. Sasaki S. Fujii H. Furuyama M. Kakeya I. Kadowaki K.

出版者

American Physical Society

雑誌

Physical review B (ISSN:01631829)

巻号頁・発行日

vol.67, no.9, pp.094507, 2003-03

被引用文献数

31 37

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We synthesized single crystalline MgB2 under ambient pressure by using conventional materials and equipment. The single crystals of MgB2 were of good quality, where the crystal structure refinements were successfully converged with R=0.020. The measurements of the magnetic properties yielded a sharp superconducting transition at 38 K with transition width ΔTc=0.8 K. The upper critical field for applied field parallel to the ab plane (Hc2ab) reveals a positive curvature, while Hc2 parallel to the c axis (Hc2c) increases linearly in temperature dependence, which yields a temperature dependence of the superconducting anisotropy ratio of γ=Hc2ab/Hc2c with γ∼1 near Tc and 4.0 at 25 K.

著者

Kaminski A. Rosenkranz S. Fretwell H. M. Mesot J. Randeria M. Campuzano J. C. Norman M. R. Li Z. Z. Raffy H. Sato T. Takahashi T. Kadowaki K.

出版者

American Physical Society

雑誌

Physical review B (ISSN:01631829)

巻号頁・発行日

vol.69, pp.212509, 2004-06

被引用文献数

31 34

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One of the interesting features of the photoemission spectra of the high temperature cuprate superconductors is the presence of a large signal (referred to as the "background") in the unoccupied region of the Brillouin zone. Here we present data indicating that the background signal is a component of the photocurrent that is separate from the spectral function and is most likely due to strong scattering of the photoelectrons. We also present an analytical method that can be used to subtract the background signal.

著者

Baelus B. J. Kanda A. Peeters F. M. Ootuka Y. Kadowaki K.

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.71, pp.140502, 2005-04

被引用文献数

30 29

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The temperature dependence of the vortex penetration and expulsion fields in mesoscopic superconducting disks are studied. We experimentally find that the penetration field decreases with increasing temperature for all values of the vorticity. On the other hand, the temperature dependence of the expulsion fields shows two regimes: For some vortex states the expulsion field increases with temperature, while for other states it is almost temperature independent. A numerical study based on the nonlinear Ginzburg-Landau theory confirms that the former regime corresponds to multivortex states and the latter to giant vortex states. The origin of this difference is discussed.

著者

Kakeya I. Wada T. Nakamura R. Kadowaki K.

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.72, pp.014540, 2005-07

被引用文献数

14 10

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Josephson plasma excitations in the high-Tc superconductor Bi2Sr2CaCu2O8+delta have been investigated in a wide microwave frequency region (9.8–75 GHz)—in particular, in a magnetic field applied parallel to the ab plane of the single crystal. In sharp contrast to the case for magnetic fields parallel to the c axis or tilted from the ab plane, it was found that there are two kinds of resonance modes, which are split in energy and possess two distinctly different magnetic field dependences. One always lies higher in energy than the other and has a shallow minimum at about 0.8 kOe, then increases linearly with magnetic field. On the other hand, another mode begins to appear only in a magnetic field (from a few kOe and higher) and has a weakly decreasing tendency with increasing magnetic field. By comparing with a recent theoretical model the higher-energy mode can naturally be attributed to the Josephson plasma resonance mode propagating along the primitive reciprocal lattice vector of the Josephson vortex lattice, whereas the lower-frequency mode is assigned to the novel phase collective mode of the Josephson vortex lattice, which has never been observed before.

著者

Sato T. Matsui H. Takahashi T. Ding H. Yang H.-B. Wang S.-C. Fujii T. Watanabe T. Matsuda A. Terashima T. Kadowaki K.

出版者

American Physical Society

雑誌

Physical review letters (ISSN:00319007)

巻号頁・発行日

vol.91, no.15, pp.157003, 2003-10

被引用文献数

99 110

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We report a systematic high-resolution angle-resolved photoemission spectroscopy on high-Tc superconductors Bi2Sr2Can-1CunO2n+4 (n=1–3) to study the origin of many-body interactions responsible for superconductivity. For n=2 and 3, a sudden change in the energy dispersion, so called “kink”, becomes pronounced on approaching (π,0) in the superconducting state, while a kink appears only around the nodal direction in the normal state. For n=1, the kink shows no significant temperature dependence even across Tc. This could suggest that the coupling of electrons with Q=(π,π) magnetic mode is dominant in the superconducting state for multilayered cuprates, while the interactions at the normal state and that of single-layered cuprates have a different origin.

著者

Koshelev A. E. Buzdin A. I. Kakeya I. Yamamoto T. Kadowaki K.

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.83, no.22, pp.224515, 2011-06

被引用文献数

9

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In strongly anisotropic layered superconductors in tilted magnetic fields, the Josephson vortex lattice coexists with the lattice of pancake vortices. Due to the interaction between them, the dissipation of the Josephson vortex lattice is very sensitive to the presence of the pancake vortices. If the c-axis magnetic field is smaller than the corresponding lower critical field, the pancake stacks are not formed but the individual pancakes may exist in the fluctuational regime either near the surface in large-size samples or in the central region for small-size mesas. We calculate the contribution of such fluctuating pancake vortices to the c-axis conductivity of the Josephson vortex lattice and compare the theoretical results with measurements on small mesas fabricated out of Bi2Sr2CaCu2O8+δ crystals. A fingerprint of fluctuating pancakes is a characteristic exponential dependence of the c-axis conductivity observed experimentally. Our results provide strong evidence of the existence of the fluctuating pancakes and their influence on the Josephson vortex lattice dissipation.