著者

Tomimoto S. Miyasaka S. Ogasawara T. Okamoto H. Tokura Y.

出版者

American Physical Society

雑誌

Physical review B (ISSN:01631829)

巻号頁・発行日

vol.68, no.3, pp.035106, 2003

被引用文献数

38 24

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The photoinduced effect on the orbital-ordered phase in perovskite-type LaVO3 has been investigated by femtosecond time-resolved reflection spectroscopy. Large reflectivity change has been observed immediately after photoirradiation. The spectral shape and polarization dependence of the reflectivity change indicate the melting of the orbital order induced by photoexcitation. The photocarriers annihilate in about 200 fs, and the orbital order partially recovers owing to thermalization with the lattice in 2–4 ps.

著者

Tomimoto S. Nansei H. Saito S. Suemoto T. Takeda J. Kurita S.

出版者

American Physical Society

雑誌

Physical review letters (ISSN:00319007)

巻号頁・発行日

vol.81, no.2, pp.417-420, 1998-07

被引用文献数

77 58

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Self-trapped-exciton (STE) luminescence of quasi-one-dimensional halogen-bridged platinum complex [Pt(en)2] [Pt(en)2Cl2] (ClO4)4 is investigated by femtosecond time-resolved luminescence spectroscopy. In the high energy tail of the luminescence band, a fast rise and decay are seen, whereas around the luminescence peak energy a slow rise of about 500 fs is observed. This rise becomes faster at the low energy side of the band. These results are consistently explained by the cooling of prethermalized STEs, following the rapid self-trapping which is estimated to occur within 140 fs.

著者

Ohki H. Takeda K. Aoki S. Hashimoto S. Kaneko T. Matsufuru H. Noaki J. Onogi T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:15507998)

巻号頁・発行日

vol.87, no.3, pp.034509, 2013-02

被引用文献数

61

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We calculate the strange quark content of the nucleon ⟨N

著者

Nomura S. Tamura H. Yamaguchi M. Akazaki T. Hirayama Y.

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.87, no.8, pp.085318, 2013-02

被引用文献数

5 1

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We report on measurement of the electron-hole effective g-factors (geff*) depending on electron filling factors ν from magnetophotoluminescence spectroscopy at low magnetic fields B<1 T in low electron density regime in a GaAs/Al0.33Ga0.67As-gated quantum well. Enhancement of geff* at odd ν is observed. The oscillatory behavior of geff* is compared with results of a theory that takes into account the lowest-order exchange interaction of the screened Coulomb interaction. Good agreement of the observed geff* with theoretical results is obtained except ν at around 3. The enhancement of geff* at even ν with decrease in electron density has not been observed.

著者

Yanagi Kazuhiro Moriya Rieko Cuong Nguyen Thanh Otani Minoru Okada Susumu

出版者

American Physical Society

雑誌

Physical review letters (ISSN:00319007)

巻号頁・発行日

vol.110, no.8, pp.086801, 2013-02

被引用文献数

18 1

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We report clear experimental evidence for the charge manipulation of molecules encapsulated inside single-wall carbon nanotubes (SWCNTs) using electrochemical doping techniques. We encapsulated β-carotene (Car) inside SWCNTs and clarified electrochemical doping characteristics of their Raman spectra. C=C streching modes of encapsulated Car and a G band of SWCNTs showed clearly different doping behaviors as the electrochemical potentials were shifted. Electron extraction from encapsulated Car was clearly achieved. However, electrochemical characteristics of Car inside SWCNTs and doping mechanisms elucidated by calculations based on density-functional theory indicate the difficulty of charge manipulation of molecules inside SWCNTs due to the presence of strong on-site Coulomb repulsion energy at the molecules.

著者

Aoki Sinya Charron Bruno Doi Takumi Hatsuda Tetsuo Inoue Takashi Ishii Noriyoshi

出版者

American Physical Society

雑誌

Physical review D (ISSN:15507998)

巻号頁・発行日

vol.87, no.3, pp.034512, 2013-02

被引用文献数

32 9

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We construct energy-independent but nonlocal potentials above inelastic thresholds, in terms of Nambu-Bethe-Salpeter wave functions defined in quantum field theories such as QCD. As an explicit example, we consider NN→NN+nπ scattering processes for n=0,1,2,…. We show the existence of energy-independent coupled channel potentials with a nonrelativistic approximation, where momenta of all particles are small compared with their own masses. In the case of two-body inelastic scatterings such as ΛΛ→ΛΛ, NΞ, ΣΣ, on the other hand, we show that energy-independent potentials can be constructed without relying on nonrelativistic approximations. We also propose a method to extract these potentials using time dependence of general correlation functions.

著者

Cuong Nguyen Thanh Otani Minoru Okada Susumu

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.87, no.4, pp.045424, 2013

被引用文献数

14 3

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Based on first-principles total-energy calculations, we studied the energetics and electronic structure of zigzag graphene nanoribbons with nanometer-scale corners. We found that the formation energy of a short zigzag edge with a 120∘ corner is substantially smaller than that of a straight zigzag edge with an infinite length. We also found that zigzag graphene ribbons with 120∘ corners are semiconductors for which the band-gap decreases with increasing length between adjacent corners. The edge state is absent for zigzag graphene ribbons with short corner-corner distances, while the edge state emerges for zigzag ribbons that have a corner-corner distance greater than 1.5 nm. The remarkable stability of the 120∘ corner of the short zigzag edges is in good agreement with the experimental observation of such corners of graphene edges.

著者

Yonezawa Shingo Kajikawa Tomohiro Maeno Yoshiteru

出版者

American Physical Society

雑誌

Physical Review Letters (ISSN:00319007)

巻号頁・発行日

vol.110, no.7, 2013-02

被引用文献数

94

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ルテニウム酸化物における超伝導の一次相転移の発見 -超伝導と磁場の未知の相互作用メカニズムの存在を示唆-. 京都大学プレスリリース. 2013-02-15.

著者

Zhao Jialong Nair Selvakumar V. Masumoto Yasuaki

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.63, no.3, pp.033307, 2001-01

被引用文献数

7 11

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The size dependence of excitonic states and vibrational modes in CuCl cubic quantum dots embedded in NaCl crystals was studied by means of site-selective persistent spectral hole burning spectroscopy. It is shown that the interaction of the longitudinal optical (LO) phonon with the exciton results in the formation of coupled exciton-phonon modes when the energy of the LO phonon approaches the energy spacings between the ground and excited states of the exciton. The energy anticrossings of the LO phonon modes with two higher optically allowed excited states of the exciton in CuCl QD’s were clearly observed at confinement energies of about 10 and 6 meV, respectively. In addition, the linewidth of the LO phonon sideband in CuCl QD’s in NaCl crystals was found to increase abruptly from 0.3 meV to about 1.2 meV at a confinement energy of about 23 meV, which appears to result from the exciton-phonon mixing of the LO phonon mode with the first excited state of the exciton. The experimental results are qualitatively understood by the LO phonon renormalization theory.

著者

Ignatiev Ivan V. Kozin Igor E. Davydov Valentin G. Nair Selvakumar V. Lee Jeong-Sik Ren Hong-Wen Sugou Shigeo Masumoto Yasuaki

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.63, no.7, pp.075316, 2001-02

被引用文献数

38 48

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Phonon resonances observed in the photoluminescence (PL) spectra of InP and In0.35Ga0.65As self-assembled quantum dots (QD’s) in an external electric field are studied in detail. The resonances are shown to arise from fast phonon-assisted relaxation of hot carriers, and to become observable when the PL is quenched by nonradiative losses from excited states. A simple model is developed that considers tunneling of the carriers from the QD’s into the barrier layer as the main process responsible for PL quenching in the presence of an electric field. From this model, the depth of the potential well for holes is estimated to be 10–20 meV for the InP QD’s. The PL kinetics measurement is performed with a time resolution of 6 ps. Clear evidence of surprisingly fast carrier relaxation with emission of high-energy acoustic phonons is found. Further acceleration of the carrier relaxation is observed under strong optical pumping. We consider this effect to be caused by Auger-like carrier-carrier scattering processes. Acceleration of the relaxation observed at elevated temperatures is ascribed to stimulated phonon emission.

著者

Ryu Shinsei Hatsugai Yasuhiro

出版者

American Physical Society

雑誌

Physical review B (ISSN:01631829)

巻号頁・発行日

vol.63, no.23, pp.233307, 2001-05

被引用文献数

9 9

---

The zero-mode wave function of a massless Dirac fermion in the presence of a random gauge field is studied. The density correlation function is calculated numerically, and found to exhibit a power law in the weak randomness with a disorder-dependent exponent. It deviates from the power law, and the disorder dependence becomes frozen in the strong randomness. A classical statistical system is employed through the replica trick to interpret the results, and the direct evaluation of the replica limit is demonstrated numerically. Analytical expressions of the correlation function and the free energy are also discussed with the replica symmetry breaking and the Liouville field theory.

著者

Matsumoto Takahiro Suzuki Jun-ichi Ohnuma Masato Kanemitsu Yoshihiko Masumoto Yasuaki

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.63, no.19, pp.195322, 2001-05

被引用文献数

62

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The optical absorption spectrum in nanocrystalline silicon (n-Si) was determined from both light transmittance and reflectance measurements. We observed that n-Si has a phonon structure in the optical absorption spectrum. This structure originates from momentum-conserving TO phonon absorption and emission, and provides direct evidence that n-Si is an indirect-band-gap semiconductor with quantum size effects. By using small-angle x-ray scattering to measure the nanocrystal size distribution, we found that the band-gap widening varies as (1/L)1.6 with decreasing nanocrystal diameter L.

著者

Tokunaga Eiji Ivanov A. L. Nair Selvakumar V. Masumoto Yasuaki

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.63, no.23, pp.233203, 2001-06

被引用文献数

11 6

---

We report observation of the inverse polariton series and a detailed experimental study of the exciton components in polaritons (Hopfield coefficients). Spontaneous emission of excitonic molecules into outgoing polaritons associated with the i(=1,2,3,4,5)th exciton states in bulk CuCl is detected and analyzed by the bipolariton model. Because the intensities of the emission lines, which form the inverse polariton series, are determined by the exciton components in the final-state polaritons, we are able to measure the Hopfield coefficients for the highly composite outgoing polaritons. Quantum interference in the optical decay of excitonic molecules, due to the multiple exciton components in the polariton and biexciton states, is also demonstrated.

著者

Tokunaga Eiji Kurihara Kazuyoshi Baba Motoyoshi Masumoto Yasuaki Matsuoka Masahiro

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.64, no.4, pp.045209, 2001-07

被引用文献数

10 9

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Radiative decay of biexcitons wave-vector (K) selectively generated in a low-K region (0<~

著者

Ryu Shinsei Hatsugai Yasuhiro

出版者

American Physical Society

雑誌

Physical review B (ISSN:01631829)

巻号頁・発行日

vol.65, no.3, pp.033301, 2001-12

被引用文献数

18

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The Dirac fermion in the random chiral models is studied, which includes the random gauge field model and the random hopping model. We focus on a connection between continuum and lattice models to give a clear perspective for the random chiral models. Two distinct structures of density of states around zero energy, one is a power-law dependence on energy in the intermediate energy range and the other is a peak at zero energy, are revealed by an extensive numerical study for large systems up to 250×250. For the random hopping model, the above findings reconcile previous inconsistencies between the lattice and the continuum models.

著者

Tomimoto Shinichi Saito Shingo Suemoto Tohru Takeda Jun Kurita Susumu

出版者

American Physical Society

雑誌

Physical review B (ISSN:01631829)

巻号頁・発行日

vol.66, no.15, pp.155112, 2002

被引用文献数

52

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The temporal evolution of the photoexcited state in quasi-one-dimensional (1D) halogen-bridged platinum complexes [Pt(en)2][Pt(en)2X2](ClO4)4 (abbreviated as Pt-X, X=Cl, Br or I), has been comprehensively studied by femtosecond time-resolved luminescence spectroscopy. In Pt-Cl, new short-lived hot luminescence is found in the low-energy side of a self-trapped exciton (STE) luminescence band. The overall behavior of the STE luminescence band within 2 ps is well explained by the vibrational relaxation of the STE. The behavior is reproduced by a model calculation based on wave packet propagation on an interaction mode composed of frequency-dispersed bulk phonons. This model is also applied to the previous results in Pt-Br. For both Pt-Cl and Pt-Br, the frequency spectra of phonons which compose the interaction mode have been estimated. In Pt-I, the STE luminescence decays much faster than those in Pt-Cl and Pt-Br, showing existence of more effective nonradiative decay channel.

著者

Otsuka Y. Hatsugai Y.

出版者

American Physical Society

雑誌

Physical review B (ISSN:01631829)

巻号頁・発行日

vol.65, no.7, pp.073101, 2002-01

被引用文献数

15

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Effects of the electron-electron interaction in the two-dimensional flux phase are investigated. We treat the half-filled Hubbard model with a magnetic flux π per plaquette by the quantum Monte Carlo method. When the interaction is small, an antiferromagnetic long-range order does not exist. It suggests that the Mott transition occurs at finite strength of the interaction in the flux phase, which is in contrast to the standard Hubbard model.

著者

Gerlovin I. Ya. Dolgikh Yu. K. Eliseev S. A. Ovsyankin V. V. Efimov Yu. P. Petrov V. V. Ignatiev I. V. Kozin I. E. Masumoto Y.

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.65, no.3, pp.035317, 2002-01

被引用文献数

21 17

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Picosecond kinetics of polarized resonant photoluminescence (PL) of HH excitons in the GaAs/AlGaAs superlattices is studied in an external magnetic field. The measurements were made in real time using a streak camera. For the magnetic field aligned along the heterostructure growth direction, the resonant PL exhibits oscillations in the degree of linear polarization. The oscillations are ascribed to quantum beats between sublevels of the optically active excitonic doublet split by the magnetic field. For the magnetic field aligned along the plane of the layers, the resonant PL is found to exhibit oscillations in circular polarization. These oscillations are related to beats between states of the optically active and optically inactive excitonic doublets. Experimental dependence of the oscillation frequency on the magnetic field strength and orientation has allowed us to determine the hole and electron g factors and the electron-hole exchange energy. Dynamics of the degree of circular polarization of the PL in magnetic field is used to measure the energy relaxation rate of the exciton spin states. In the magnetic field exceeding 1 T, the energy relaxation rate is shown to be magnetic-field independent and equal (1±0.2)×1010 s-1. This value is found to be much smaller than the spin phase relaxation rate determined from decay of the quantum beats in linear polarization. Unlike the energy relaxation rate, the latter grows linearly with the field strength and equals (5±0.5)×1010 s-1 at 5 T. It is concluded that the main mechanism responsible for loss of macroscopic spin coherence is the reversible dephasing within inhomogeneously broadened system.

著者

Li Y. J. Takeuchi O. Futaba D. N. Oigawa H. Miyake K. Shigekawa H. Kuk Y.

出版者

American Physical Society

雑誌

Physical review B (ISSN:01631829)

巻号頁・発行日

vol.65, no.11, pp.113306, 2002-03

被引用文献数

3

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Site-dependent adsorption structures of Xe atoms on a Si(111)-7×7 surface were studied by scanning tunneling microscopy at 8 K. Xe atoms initially adsorb as dimers on the site between a rest atom and its two neighboring center adatoms, and then near the corner adatom site. Similar structures were formed at both the faulted half (FH) and the unfaulted half (UH) of the 7×7 unit. The observed structure is in excellent agreement with that estimated by the rigid ball model, however, site-dependent bias dependence and different stabilities were observed for them, indicating the existence of different interactions between Xe and Si atoms in the 7×7 unit despite the stable electronic structure of Xe. Based on the results with thermal desorption spectroscopy, the adsorption energies are estimated to be 200 and 220 meV for FH and UH units, respectively.

著者

Kozin I. E. Davydov V. G. Ignatiev I. V. Kavokin A. V. Kavokin K. V. Malpuech G. Ren Hong-Wen Sugisaki M. Sugou S. Masumoto Y.

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.65, no.24, pp.241312, 2002-06

被引用文献数

61 53

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Spins of resident electrons in charged quantum dots (QD’s) act as local magnets inducing the Zeeman splitting of excitons trapped into dots. This is evidenced by the observation of quantum beats in the linearly polarized time-resolved photoluminescence of a biased array of self-assembled InP QD’s. An external magnetic field is found to shorten the spin beats’ decay time keeping constant the frequency of the beats. A model using the pseudospin formalism allows one to attribute the observed quantum beats to the radiative decay of hot trions having two electrons that occupy different energy levels in a QD.