438 research outputs found

    Linear response calculation using the canonical-basis TDHFB with a schematic pairing functional

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    A canonical-basis formulation of the time-dependent Hartree-Fock-Bogoliubov (TDHFB) theory is obtained with an approximation that the pair potential is assumed to be diagonal in the time-dependent canonical basis. The canonical-basis formulation significantly reduces the computational cost. We apply the method to linear-response calculations for even-even nuclei. E1 strength distributions for proton-rich Mg isotopes are systematically calculated. The calculation suggests strong Landau damping of giant dipole resonance for drip-line nuclei.Comment: 6 pages, 1 figure, INPC 2010 conference proceding

    Temperature-dependent photoemission spectral weight transfer and chemical potential shift in Pr1x_{1-x}Cax_xMnO3_3 : Implications for charge density modulation

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    We have studied the temperature dependence of the photoemission spectra of Pr1x_{1-x}Cax_xMnO3_3 (PCMO) with x=0.25x=0.25, 0.3 and 0.5. For x=0.3x=0.3 and 0.5, we observed a gap in the low-temperature CE-type charge-ordered (CO) phase and a pseudogap with a finite intensity at the Fermi level (EFE_F) in the high-temperature paramagnetic insulating (PI) phase. Within the CO phase, the spectral intensity near EFE_F gradually increased with temperature. These observations are consistent with the results of Monte Carlo simulations on a model including charge ordering and ferromagnetic fluctuations [H. Aliaga {\it et al.} Phys. Rev. B {\bf 68}, 104405 (2003)]. For x=0.25x=0.25, on the other hand, little temperature dependence was observed within the low-temperature ferromagnetic insulating (FI) phase and the intensity at EFE_F remained low in the high-temperature PI phase. We attribute the difference in the temperature dependence near EFE_F between the CO and FI phases to the different correlation lengths of orbital order between both phases. Furthermore, we observed a chemical potential shift with temperature due to the opening of the gap in the FI and CO phases. The doping dependent chemical potential shift was recovered at low temperatures, corresponding to the disappearance of the doping dependent change of the modulation wave vector. Spectral weight transfer with hole concentration was clearly observed at high temperatures but was suppressed at low temperatures. We attribute this observation to the fixed periodicity with hole doping in PCMO at low temperatures.Comment: 5pages, 7figure

    Chemical potential shift induced by double-exchange and polaronic effects in Nd_{1-x}Sr_xMnO_3

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    We have studied the chemical potential shift as a function of temperature in Nd1x_{1-x}Srx_xMnO3_3 (NSMO) by measurements of core-level photoemission spectra. For ferromagnetic samples (x=0.4x=0.4 and 0.45), we observed an unusually large upward chemical potential shift with decreasing temperature in the low-temperature region of the ferromagnetic metallic (FM) phase. This can be explained by the double-exchange (DE) mechanism if the ege_g band is split by dynamical/local Jahn-Teller effect. The shift was suppressed near the Curie temperature (TCT_C), which we attribute to the crossover from the DE to lattice-polaron regimes.Comment: 5 pages, 6 figure

    Depth profile photoemission study of thermally diffused Mn/GaAs (001) interfaces

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    We have performed a depth profile study of thermally diffused Mn/GaAs (001) interfaces using photoemission spectroscopy combined with Ar+^+-ion sputtering. We found that Mn ion was thermally diffused into the deep region of the GaAs substrate and completely reacted with GaAs. In the deep region, the Mn 2pp core-level and Mn 3dd valence-band spectra of the Mn/GaAs (001) sample heated to 600 ^{\circ}C were similar to those of Ga1x_{1-x}Mnx_xAs, zinc-blende-type MnAs dots, and/or interstitial Mn in tetrahedrally coordinated by As atoms, suggesting that the Mn 3dd states were essentially localized but were hybridized with the electronic states of the host GaAs. Ferromagnetism was observed in the dilute Mn phase.Comment: 5 pages, 4 figure

    Chemical potential landscape in band filling and bandwidth-control of manganites: Photoemission spectroscopy measurements

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    We have studied the effects of band filling and bandwidth control on the chemical potential in perovskite manganites R1xAxR_{1-x}A_xMnO3_3 (RR : rare earth, AA : alkaline earth) by measurements of core-level photoemission spectra. A suppression of the doping-dependent chemical potential shift was observed in and around the CE-type charge-ordered composition range, indicating that there is charge self-organization such as stripe formation or its fluctuations. As a function of bandwidth, we observed a downward chemical potential shift with increasing bandwidth due to the reduction of the orthorhombic distortion. After subtracting the latter contribution, we found an upward chemical potential shift in the ferromagnetic metallic region 0.3<x<0.50.3<x<0.5, which we attribute to the enhancement of double-exchange interaction involving the Jahn-Teller-split ege_g band.Comment: 5 pages, 4 figure

    Study of pygmy dipole resonance with a new time-dependent mean field theory

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    We carry out a systematic investigation on the low-energy electric dipole strength, which is often called pygmy dipole resonances (PDR), using the canonical-basis time-dependent Hartree-Fock-Bogoliubov (Cb-TDHFB) method. The Cb-TDHFB is a new method which is derived from TDHFB with an approximation analogous to the BCS theory that the pair potential is assumed to be diagonal in the time-dependent canonical basis. We apply the method to linear-response calculation for even-even nuclei. We report the neutron-number dependence of PDR in light (A 100) around N = 82.Comment: 6 pages, 3 figures, Rutherford Centennial Conference on Nuclear Physics conference proceeding

    Chemical potential shift and spectral weight transfer in Pr1x_{1-x}Cax_xMnO3_3 revealed by photoemission spectroscopy

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    We have studied the chemical potential shift and changes in the electronic density of states near the Fermi level (EFE_F) as a function of carrier concentration in Pr1x_{1-x}Cax_xMnO3_3 (PCMO, 0.2x0.650.2 \le x \le 0.65) through the measurements of photoemission spectra. The results showed that the chemical potential shift was suppressed for x \agt 0.3, where the charge exchange (CE)-type antiferromagnetic charge-ordered state appears at low temperatures. We consider this observation to be related to charge self-organization such as stripe formation on a microscopic scale in this composition range. Together with the previous observation of monotonous chemical potential shift in La1x_{1-x}Srx_xMnO3_3, we conclude that the tendency toward the charge self-organization increases with decreasing bandwidth. In the valence band, spectral weight of the Mn 3dd ege_g electrons in PCMO was transferred from \sim 1 eV below EFE_F to the region near EFE_F with hole doping, leading to a finite intensity at EFE_F even in the paramagnetic insulating phase for x \agt 0.3, probably related with the tendency toward charge self-organization. The finite intensity at EFE_F in spite of the insulating transport behavior is consistent with fluctuations involving ferromagnetic metallic states.Comment: 6 pages, 5 figure

    S1 excited-state dynamics of OMpCA and its hydrogen-bonded complexes

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    第30回化学反応討論会, 2014年6月4日-6日, イーグレひめじ(姫路

    Folding catastrophes due to viscosity in multiferroic domains : implications for room-temperature multiferroic switching

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    Unusual domains with curved walls and failure to satisfy the Landau–Lifshitz-Kittel Law are modeled as folding catastrophes (saddle-node bifurcations). This description of ballistic motion in a viscous medium is based upon early work by Dawber et al 2003 Appl. Phys. Lett . 82 436. It suggests that ferroelectric films can exhibit folds or vortex patterns but not both.Publisher PDFPeer reviewe
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