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.

著者

Hatsugai Y. Ryu S.

出版者

American Physical Society

雑誌

Physical review B (ISSN:01631829)

巻号頁・発行日

vol.65, no.21, pp.212510, 2002-06

被引用文献数

13 13

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Topological quantum phase transitions in superconductivity are discussed on two-dimensional lattices. The main focus is on the Chern number for superconducting states. Each superconductivity is characterized by the Chern number, and the quantum phase transition is associated with topological changes of the quasiparticle Bloch function in the Brillouin zone. For the superconducting case, the Chern number has several equivalent but different topological expressions given by vortices, the Dirac monopole, and strings. We demonstrate quantum phase transitions by these topological quantities both for singlet and triplet cases.

著者

Brouwer P. W. Racine E. Furusaki A. Hatsugai Y. Morita Y. Mudry C.

出版者

American Physical Society

雑誌

Physical review B (ISSN:01631829)

巻号頁・発行日

vol.66, no.1, pp.014204, 2002-07

被引用文献数

32

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If the number of lattice sites is odd, a quantum particle hopping on a bipartite lattice with random hopping between the two sublattices only is guaranteed to have an eigenstate at zero energy. We show that the localization length of this eigenstate depends strongly on the boundaries of the lattice, and can take values anywhere between the mean free path and infinity. The same dependence on boundary conditions is seen in the conductance of such a lattice if it is connected to electron reservoirs via narrow leads. For any nonzero energy, the dependence on boundary conditions is removed for sufficiently large system sizes.

著者

Otsuka Y. Morita Y. Hatsugai Y.

出版者

American Physical Society

雑誌

Physical review B (ISSN:01631829)

巻号頁・発行日

vol.66, no.7, pp.073109, 2002-08

被引用文献数

7

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We investigate anisotropic charge fluctuations in the two-dimensional Hubbard model at half-filling. By the quantum Monte Carlo method, we calculate a momentum-resolved charge compressibility κ(k)=d〈n(k)〉/dμ, which shows the effects of an infinitesimal doping. At the temperature T∼t2/U, κ(k) shows a peak structure at the (±π/2,±π/2) points along the

著者

Sakai S. Tanimoto H. Kita E. Mizubayashi H.

出版者

American Physical Society

雑誌

Physical review B (ISSN:01631829)

巻号頁・発行日

vol.66, no.21, pp.214106, 2002-12

被引用文献数

16 17

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Nanocrystalline (n) Au specimens with a density of 19.4±0.2 g/cm3 and a mean grain size of about 20 nm were prepared below 300 K by the gas deposition method, where two types of n-Au specimens were obtained as a function of a deposition rate, the type-H specimens above 800 nm/s and the type-L specimens below 800 nm/s. The anelastic and the plastic creep responses are similar qualitatively but different quantitatively between the type-H and type-L specimens. The anelastic strain ɛan,GB, associated with the grain boundary (GB) regions, increases linearly with (T-Tan1)(σap-σan1), when the temperature T is higher than a threshold temperature Tan1 of 200 K and the applied stress σap is higher than a threshold stress, σan1, of a few MPa. The ratio of ɛan,GB to the elastic strain is as large as 1.1 for the type-H specimens and 0.2 for the type-L specimens at 320 K for σap≫σan1. The activation energy for the GB anelastic process is 0.2 eV. We surmise that cooperative motions of many atoms in the GB regions are responsible for ɛan,GB, and both Tan1 and σan1 show a distribution depending on the number of atoms associated. The plastic creep rate ɛ′ vs σap data show a letter S-like curve. We classified the creep response into three categories, region I for the linear creep rate region for σap between σpc 1 and σpc2, region II for the transient creep rate region for σap between σpc2 and σpc3, and region III for the saturation creep rate region for σap between σpc3 and σy. The threshold stresses σpc1 and σpc2 and the yield stress σy are about 30, 150, and 360 MPa for the type-H specimens, and about 60, 300, and 500 MPa for the type-L specimens, respectively. σpc3 is slightly lower than σy. From scanning tunneling microscopy images, we surmise that the localized GB slip takes place in region I, and the mean separation between the localized GB slips decreases with increasing σap in region II and becomes comparable with the mean grain size in region III. The plastic creep in region III may be explained by the Ashby creep. The present view for the creep behavior explains the low-temperature creep behavior of fcc n metals.

著者

Yugova I. A. Gerlovin Ya. Davydov V. G. Ignatiev I. V. Kozin I. E. Ren H. W. 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.66, no.23, pp.235312, 2002-12

被引用文献数

37 36

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The paper reports on quantum beats observed in the photoluminescence kinetics of a single layer of the InPself-assembled quantum dots in a magnetic field. It is found that the beats arise only after removal of excesscharges from the quantum dots by an external electrical bias. The quantum beats are shown to be related to theinterference of the excitonic fine-structure states split by the magnetic-field. The dependences of the beatcharacteristics on the magnetic-field strength and orientation are studied. Theoretical analysis based on a modelspin Hamiltonian has allowed us to describe adequately the shape of the oscillating component of the signal.We have determined the values of the electron g-factor components and estimated the spread and the meanvalue of the hole g factor, as well as of the electron-hole exchange splitting parameters.

著者

竹内 紀仁 山村 高淑

出版者

北海道大学大学院国際広報メディア・観光学院 観光創造専攻 文化資源デザイン研究室 (コンテンツツーリズム研究会)

雑誌

コンテンツツーリズム論叢 : Collected Treatises on Contents Tourism

巻号頁・発行日

vol.1, pp.6-11, 2012-08-12

著者

嶋村 紘輝

出版者

早稲田商学同攻会

雑誌

早稲田商学=The Waseda commercial review (ISSN:03873404)

巻号頁・発行日

vol.262号, pp.77-100, 1977-02

著者

朴 鎮洙

出版者

名古屋大学高等教育研究センター

巻号頁・発行日

2012 (Released:2012-03-19)

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2011年度名古屋大学学生論文コンテスト優秀賞受賞

著者

陳 霊佳

出版者

東京大学大学院新領域創成科学研究科環境学研究系社会文化環境学専攻

巻号頁・発行日

2010-03-24

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報告番号: ; 学位授与年月日: 2010-03-24 ; 学位の種別: 修士 ; 学位の種類: 修士(環境学) ; 学位記番号: 修創域第3558号 ; 研究科・専攻: 新領域創成科学研究科社会文化環境学専攻

著者

松丸 壽雄

出版者

京都大学

巻号頁・発行日

2007-11-26

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新制・論文博士

著者

瀬川 信久

出版者

北海道大学大学院法学研究科

雑誌

北大法学論集 (ISSN:03855953)

巻号頁・発行日

vol.53, no.2, pp.294-282, 2002-07-11

著者

禹 暎均

出版者

北海道大学農学部農業経済学科

雑誌

北海道大学農經論叢 (ISSN:03855961)

巻号頁・発行日

vol.44, pp.97-114, 1988-02

著者

加瀬 和俊

出版者

東京大学社会科学研究所

雑誌

社會科學研究 (ISSN:3873307)

巻号頁・発行日

vol.58, no.1, pp.125-155, 2006-09-30

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戦前日本に失業保険制度は存在しなかったが, そのための諸構想は存在し, その一部は法案として議会に提出された.また, 失業保険形態の給付制度は小規模なものではあれ大都市自治体によって実施された.本稿は, それらの諸構想・諸制度を比較し, 諸構想が英独等の制度を参考にしながらも日本資本主義に許容可能な種々の制度的工夫を案出していたことを確認した.実施された日雇共済制度については, 保険形態をとりつつも実質的には公的扶助であり, 赤字削減のための制度的工夫が制度の利用減と休眠化を招いたプロセスを示した.また1920年代には貯蓄奨励制度的な失業給付を容認していた資本家団体が, 1930年代には失業保険形態をとる全制度に反対するにいたった経過を明らかにした.

著者

Morishita M. Nagatani H.

出版者

American Physical Society

雑誌

Physical review B (ISSN:10980121)

巻号頁・発行日

vol.65, no.10, pp.104524, 2002-03

被引用文献数

15

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Nuclear-spin heat capacities of submonolayer solid 3He adsorbed on a graphite surface are measured down to 100 μK, a factor of 20 lower temperature than in previous works. This system is one of the most ideal two-dimensional quantum spin systems (S=1/2). In a wide areal density region (6.1 nm-2<~ρ<~8.7 nm-2), anomalous temperature dependencies of the heat capacity, C∝Tα(-1.6≲α≲-0.7), are observed in a temperature range over two orders of magnitude (0.1 mK<~T<~20 mK) instead of the expected high-temperature behavior (α=-2) for localized spins. The α value shows a complicated density dependence which is accompanied by a density variation of a heat capacity isotherm at an extremely low temperature (=0.2 mK). This anomaly is similar to the previously observed high-temperature behavior (α≈-1) of the lowest density solid in the second layer. Although quantitative explanations are lacking for these anomalies, they are likely due to the high frustration caused by competing ferromagnetic and antiferromagnetic multiple-spin exchange interactions at least up to the six-spin exchange. We find that the excess heat-capacity (Cex) due to the amorphous 3He adsorbed on substrate heterogeneities is certainly not an origin of the anomalous behavior in C of the uniform submonolayer. Only at and below the density for the sqrt[3]×sqrt[3] commensurate phase (ρ=6.4 nm-2) heat capacity bumps at around 20 mK are observed. We suggest the possibility of spin-polaron effects caused by delocalized vacancies to explain this anomaly.

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

Aoki Sinya Fukaya Hidenori Hashimoto Shoji Onogi Tetsuya

出版者

American Physical Society

雑誌

Physical review D (ISSN:15507998)

巻号頁・発行日

vol.76, no.5, pp.054508, 2007-09

被引用文献数

85 93

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In finite volume the partition function of QCD with a given theta is a sum of different topological sectors with a weight primarily determined by the topological susceptibility. If a physical observable is evaluated only in a fixed topological sector, the result deviates from the true expectation value by an amount proportional to the inverse space-time volume 1/V. Using the saddle point expansion, we derive formulas to express the correction due to the fixed topological charge in terms of a 1/V expansion. Applying this formula, we propose a class of methods to determine the topological susceptibility in QCD from various correlation functions calculated in a fixed topological sector.