Search results for: S. Onari

Items from 1 to 20 out of 28 results

article

Study of non-Fermi-liquid-like state and pairing symmetry in iron pnictides based on the multiorbital Hubbard-Holstein model

S. Onari, H. Kontani

Physica C: Superconductivity > 2011 > 471 > 21-22 > 670-674

We study the five-orbital Hubbard-Holstein model, taking account of the electron–phonon (e-ph) interaction due to the Fe-ion oscillation. In order to include the self-energy correction, we employ the fluctuation exchange (FLEX) approximation. It is revealed that the orbital fluctuations are enhanced by the e-ph interaction, which causes a strong attractive pairing interaction. The orbital fluctuations...

article

Nonmagnetic impurity effects and neutron scattering spectrum in iron pnictides

S. Onari, H. Kontani

Physica C: Superconductivity > 2010 > 470 > 20 > 1007-1009

We study the effect of local impurity and the neutron scattering spectrum based on the five-orbital model obtained by the first principle calculation for iron pnictides. We find that the interband impurity scattering is induced by the complex multiorbital structure. This fact means that the fully-gapped sign-reversing s-wave state, which is predicted by spin-fluctuation theories, is very fragile against...

article

Spin Hall effect in a curved graphene with spin–orbit interaction

T. Kato, S. Onari, J. Inoue

Physica E: Low-dimensional Systems and Nanostructures > 2010 > 42 > 4 > 729-731

The effect of a curvature in a graphene with a spin–orbit interaction (SOI) is studied using a realistic π and σ orbital tight-binding (TB) model. The coupling of the atomic SOI and the curvature-induced orbital mixing produces an effective Rashba-type SOI and causes the k-dependent energy splitting in the low-energy electronic structure near the K point. We find that the spin Hall effect (SHE) is...

article

Odd-frequency superconductivity on quasi-one-dimensional triangular lattice in the Hubbard model

K. Shigeta, S. Onari, K. Yada, Y. Tanaka

Physica C: Superconductivity and its applications > 2009 > 469 > 15-20 > 988-990

We study the superconductivity in the Hubbard model on quasi-one-dimensional triangular lattice using random phase approximation (RPA). We find that odd-frequency spin-singlet p-wave pairing can be realized on isosceles quasi-one-dimensional triangular lattice.

article

Theory of tunneling spectroscopy in LaFeAsO1-xFx

S. Onari, Y. Tanaka

Physica C: Superconductivity and its applications > 2009 > 469 > 15-20 > 912-914

We calculate the surface density of state of iron based LaFeAsO1-xFx superconductor. The gap function is obtained microscopically by solving the Eliashberg equation in a 5-band Hubbard model with the random phase approximation (RPA). Although the gap function has a sign change between Fermi surfaces, we cannot find zero bias conductance peak for [100] and [110]-oriented interface.

article

Odd-frequency pairings in a non-centrosymmetric system

K. Yada, S. Onari, Y. Tanaka

Physica C: Superconductivity and its applications > 2009 > 469 > 15-20 > 991-994

We study possible pairing symmetries of non-centrosymmetric superconductors in the Hubbard model with the Rashba-type spin–orbit interaction (RSOI). Because of the breakdown of space inversion symmetry due to RSOI, a mixture of pairing states with different symmetries can emerge. We find that the RSOI mixes not only the spin-singlet even-parity pairing and spin-triplet odd-parity pairings with even-frequency...

article

Superconductivity under uniaxial compression in β-(BDA-TTP) salts

T. Suzuki, S. Onari, H. Ito, Y. Tanaka

Physica C: Superconductivity and its applications > 2009 > 469 > 15-20 > 979-981

In order to clarify the mechanism of organic superconductor β-(BDA-TTP) salts. We study the superconductivity under uniaxial compression with non-dimerized two-band Hubbard model. We have calculated the uniaxial compression dependence of T _c by solving the Eliashberg’s equation using the fluctuation exchange (FLEX) approximation. The transfer integral under the uniaxial compression was estimated...

article

Unified origin for superconductivity, magnetism, and large thermopower in NaxCoO2

K. Kuroki, R. Arita, S. Okubo, T. Nojima, more

Journal of Physics and Chemistry of Solids > 2008 > 69 > 12 > 3360-3364

We argue that the large thermopower, magnetism, and superconductivity observed in NaxCoO2 share the same origin, namely, the peculiar shape of the a1g band. Superconductivity and magnetism arise from the local minimum structure of the band at the Γ point, while the thermopower originates from the overall “pudding mold” shape of the band. Our study shows the importance of the band structure and the...

article

Fluctuation exchange study on the double chain superconductor Pr2Ba4Cu7O15-δ

T. Nakano, K. Kuroki, S. Onari

Physica B: Physics of Condensed Matter > 2008 > 403 > 5-9 > 1159-1161

Superconductivity of a double chain superconductor Pr2Ba4Cu7O15-δ is investigated on the double chain Hubbard model with realistic values of the hopping parameters, on-site interaction U, and off-site interaction V. By applying the fluctuation exchange (FLEX) method to the model and solving the linearized Eliashberg's equation, singlet pairing superconducting phase, which has the doping dependence...

article

Unified origin for superconductivity and 3D magnetism in NaxCoO2

K. Kuroki, S. Okubo, T. Nojima, H. Usui, more

Physica B: Physics of Condensed Matter > 2008 > 403 > 5-9 > 1151-1153

We argue that the spin fluctuations that give rise to superconductivity in NaxCoO2·yH2O and the 3D magnetism in the non-hydrated NaxCoO2 share the same origin. Due to the local minimum of the a1g band at the Γ point, inner and outer portions of the Fermi surface arise, where the nesting between the two results in these interesting phenomena.

article

Quasiparticle density of states in high-Tc superconductors in the superconducting state

T. Hata, S. Onari, S. Honda, H. Itoh, more

Physica C: Superconductivity and its applications > 2007 > 463-465 > Complete > 123-125

In order to clarify the tunneling spectroscopy in hole-doped high-T _c cuprates, we study the strongly correlated electron systems with surface using the 2D Hubbard model with fluctuation exchange (FLEX) approximation from the side of weak coupling theory. We have found that (i) LDOS near the (1,1,0) surface has a zero energy peak, and (ii) LDOS is asymmetric, reflecting the asymmetry of band...

article

Anomalous transport phenomena in CeCoIn5 close to quantum critical point

S. Onari, H. Kontani, Y. Tanaka

Journal of Magnetism and Magnetic Materials > 2007 > 310 > 2 Part 1 > 359-361

Various transport coefficients show striking deviations from conventional Fermi-liquid behaviors in many electron systems which are close to antiferromagnetic (AF) quantum critical points (QCP). For example, Hall coefficients and Nernst coefficients in three-dimensional heavy fermion CeCoIn5 and CeCu6-xAux increase remarkably at low temperatures. These temperature dependences are too strong to explain...

article

Lattice vibrations of pure and doped GaSe

K. Allakhverdiev, T. Baykara, Ş. Ellialtioğlu, F. Hashimzade, more

Materials Research Bulletin > 2006 > 41 > 4 > 751-763

The Bridgman method is used to grow especially undoped and doped single crystals of GaSe. Composition and impurity content of the grown crystals were determined using X-ray fluorescence (XRF) method. X-ray diffraction, Raman scattering, photoluminescence (PL), and IR transmission measurements were performed at room temperature. The long wavelength lattice vibrations of four modifications of GaSe were...

article

Spectroscopic investigations of the photo-induced structural transformation of C ₆ ₀ single crystals under high pressure

T. Mitani, K. Matsuishi, S. Onari

Chemical Physics Letters > 2004 > 383 > 5-6 > 486-490

Photo-induced structural transformations of C ₆ ₀ single crystals under pressures up to 30 GPa were investigated by means of optical transmittance and photoluminescence. We found that the band gap energy shifts toward lower energies at a rate of -16 meV/GPa with an increase in the pressure applied during photo-irradiation. The activation energy of the photo-induced structural transformation...

article

Raman scattering under pressure in ZnGa ₂ Se ₄

K. Allakhverdiev, F. Gashimzade, T. Kerimova, T. Mitani, more

Journal of Physics and Chemistry of Solids > 2003 > 64 > 9-10 > 1597-1601

The Raman scattering spectra of ZnGa ₂ Se ₄ under pressure were investigated at 300 K up to 18.9 GPa. Two stages were observed in the pressure dependences of Raman bands. Such behavior in accordance with the experimental findings existing in literature and was attributed as arising due to the order-disorder phase transition in the cation sublattice.Using the Harrison-Keating's model...

article

Temperature dependence of photoluminescence from mono-dispersed Si nanoparticles

T. Orii, M. Hirasawa, T. Seto, N. Aya, more

The European Physical Journal D > 2003 > 24 > 1-3 > 119-122

The temperature dependence of photoluminescence (PL) from mono-dispersed Si nanoparticles was studied from 4 to 300 K. Si nanoparticles produced by pulsed laser ablation in He background gas were sorted into the 6 nm size range by a differential mobility analyzer (DMA). The spread of the size distribution was narrowed to a geometrical standard deviation g = 1.05. On decreasing the temperature from...

article

Low frequency Raman scattering of amorphous Ge ₁ _- _x S _x (0=<x=<0.62)

H. Ogura, K. Matsuishi, S. Onari

Journal of Non-Crystalline Solids > 2002 > 299-302 > Part 2 > 973-977

Amorphous Ge ₁ _- _x S _x (0.0=<x=<0.62) films were prepared by a laser ablation method, and their low frequency Raman scattering spectra were measured at 20 K. Two distinct vibration regimes were observed in the spectra. In the regime at higher frequencies, the power-law dependence of the reduced Raman intensity (I ω ^t ) changes with an increase in x for x>0...

article

Visible photoluminescence in thermally annealed Bi implanted SiO ₂ films

M. Komatsu, K. Oyoshi, S. Hishita, K. Matsuishi, more

Materials Chemistry and Physics > 1998 > 54 > 1-3 > 286-288

Photoluminescence (PL) from Bi ⁺ implanted SiO ₂ films prepared by thermal oxidation has been studied as a function of annealing temperature. Bi ions were implanted at room temperature with an energy of 200 keV and doses from 1 x 10 ¹ ⁴ to 1 x 10 ¹ ⁴ ions cm ^- ² . After annealing, some samples showed two broad intense PL bands with peak energies...

article

Low frequency Raman scattering in amorphous Ge _X S ₁ _- _X

H. Ogura, K. Matsuishi, S. Onari

Journal of Non-Crystalline Solids > 1998 > 227-230 > Part 2 > 761-764

The low frequency Raman scattering of amorphous Ge _X S ₁ _- _X (0.07=<X=<0.37) was measured at 20 K. Two distinct vibration regimes were observed in the reduced Raman scattering spectra after the subtraction of excess scattering. The regime at lower frequency region where the reduced Raman intensity, I _R , is proportional to ω ⁴ is assumed to be due to the...

article

Optical spectra of the correlated metallic system Ca1−xSrxVO3

H. Makino, I.H. Inoue, M.J. Rozenberg, F. Iga, more

Physica B: Physics of Condensed Matter > 1997 > 237-238 > Complete > 56-58

Optical reflectivity spectra are studied for single crystals of a perovskite-related 3d ¹ correlated metallic system Ca _1−x Sr _x VO ₃ . The measurement is made at room temperature between 0.03 and 40 eV. In the optical conductivity spectra a Drude-like contribution peaked at ω=0 and other two contributions, which may be associated with Hubbard band and a quasiparticle...

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Search results for: S. Onari

Study of non-Fermi-liquid-like state and pairing symmetry in iron pnictides based on the multiorbital Hubbard-Holstein model

Nonmagnetic impurity effects and neutron scattering spectrum in iron pnictides

Spin Hall effect in a curved graphene with spin–orbit interaction

Odd-frequency superconductivity on quasi-one-dimensional triangular lattice in the Hubbard model

Theory of tunneling spectroscopy in LaFeAsO1-xFx

Odd-frequency pairings in a non-centrosymmetric system

Superconductivity under uniaxial compression in β-(BDA-TTP) salts

Unified origin for superconductivity, magnetism, and large thermopower in NaxCoO2

Fluctuation exchange study on the double chain superconductor Pr2Ba4Cu7O15-δ

Unified origin for superconductivity and 3D magnetism in NaxCoO2

Quasiparticle density of states in high-Tc superconductors in the superconducting state

Anomalous transport phenomena in CeCoIn5 close to quantum critical point

Lattice vibrations of pure and doped GaSe

Spectroscopic investigations of the photo-induced structural transformation of C ₆ ₀ single crystals under high pressure

Raman scattering under pressure in ZnGa ₂ Se ₄

Temperature dependence of photoluminescence from mono-dispersed Si nanoparticles

Low frequency Raman scattering of amorphous Ge ₁ _- _x S _x (0=<x=<0.62)

Visible photoluminescence in thermally annealed Bi implanted SiO ₂ films

Low frequency Raman scattering in amorphous Ge _X S ₁ _- _X

Optical spectra of the correlated metallic system Ca1−xSrxVO3

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