Evidence for two energy scales in the superconducting state of optimally doped (Bi,Pb)2(Sr,La)2CuO6+delta

We use angle-resolved photoemission spectroscopy to investigate the energy gap(s) in (Bi,Pb)2(Sr,La)2CuO6+delta. We find that the spectral gap has two components in the superconducting state: a superconducting gap and pseudogap. Differences in their momentum and temperature dependence suggest that they represent two separate energy scales. Spectra near the node reveal a sharp peak with a small gap below T(c) that closes at T(c). Near the antinode, spectra are broad with a large energy gap of approximately 40 meV above and below T(c). The latter spectral shape and gap magnitude are almost constant across T(c), indicating that the pseudogap state coexists with the superconducting state below T(c), and it dominates spectra around the antinode. We speculate that the pseudogap state competes with the superconductivity by diminishing spectral weight in antinodal regions, where the superconducting gap is largest.     

Characteristics improvement of HfO2/Ge gate stack structure by fluorine treatment of germanium surface

Chemical reactivity of fluorine molecule (F₂)-germanium (Ge) surface and dissociation of fluorine (F)-Ge bonding have been simulated by semi-empirical molecular orbital method theoretically, which shows that F on Ge surface is more stable compared to hydrogen. Ge MIS (metal insulator semiconductor) capacitor has been fabricated by using F₂-treated Ge(1 0 0) substrate and HfO₂ film deposited by photo-assisted MOCVD. Interface state density observed as a hump in the C-V curve of HfO₂/Ge gate stack and its C-V hysteresis were decreased by F₂-treatment of Ge surface. XPS (X-ray photoelectron spectroscopy) depth profiling reveals that interfacial layer between HfO₂ and Ge is sub-oxide layer (GeO_x or HfGeO_x), which is believed to be origin of interface state density.F was incorporated into interfacial layer easily by using F₂-treated Ge substrate. These results suggest that interface defect of HfO₂/Ge gate stack structure could be passivated by F effectively.     

Coherent transfer of light polarization to electron spins in a semiconductor

We demonstrate that the superposition of light polarization states is coherently transferred to electron spins in a semiconductor quantum well. By using time-resolved Kerr rotation, we observe the initial phase of Larmor precession of electron spins whose coherence is transferred from light. To break the electron-hole spin entanglement, we utilized the big discrepancy between the transverse g factors of electrons and light-holes. The result encourages us to make a quantum media converter between flying photon qubits and stationary electron-spin qubits in semiconductors.     

Relaxation structure analysis of Li inserted γ-Fe2O3

γ-Fe₂O₃ has a spinel structure with cation vacancy and is expected to perform as a favorable electrode material for secondary lithium-ion battery. When lithium is inserted electrochemically into γ-Fe₂O₃, prolonged potential change is observed after the insertion. In this study, we inserted various amount of Li into γ-Fe₂O₃ (x = 0.66, 1.1, 1.5 in terms of Li_XFe₂O₃), then made the circuit open, measured X-ray diffraction (XRD) patterns at various elapsed time, and analyzed the crystal structure change of γ-Fe₂O₃ with time by the Rietveld method. The X-ray Rietveld analysis revealed that the iron occupancy of 8a site decreased and that of 16c site increased with lithium insertion process and after lithium insertion, the iron occupancy of 8a site increased and that of 16c site decreased gradually with relaxation time. It is indicated that lithium prefer 8a site to occupy kinetically, on the other hand, prefer 16c site thermodynamically.     

Atomic and molecular spectroscopy with a continuous-wave, doubly resonant, monolithic optical parametric oscillator

Doppler-broadened atomic and molecular spectra were observed with a one octave tunable, continuous-wave, doubly resonant, monolithic optical parametric oscillator (OPO) using 5% MgO-doped LiNbO₃ as a non-linear crystal with a birefringent phase-matching configuration. By tuning the frequency of a pump laser, longitudinal mode selection over 20 successive modes, corresponding to a 60 GHz span, was possible, owing to the simple structure of the monolithic OPO. Continuous frequency tuning was achieved using an external waveguide-type electrooptic phase modulator (EOM). By changing the modulation frequency of the EOM, frequency tuning of the optical sidebands over 12 GHz was possible, which is larger than the one free spectral range of the monolithic cavity of 3 GHz. We could observe the Cs-D₁ (894 nm), Cs-D₂ (852 nm), Rb-D₁ (795 nm), acetylene R9 (1520 nm) and P9 (1530 nm) transitions with the single monolithic OPO.     

Ultra-narrow interval angular control signal for holographic data storage system

Optical Review - A precise and fast method for controlling the reference-beam angle of an angular-multiplexed holographic data storage system (HDSS)—to achieve larger capacity and faster...     

N‐shell ionization cross sections by proton impact in the BEA

The N‐subshell ionizations cross sections of heavy elements by proton impact have been calculated in the binary‐encounter approximation. The momentum distribution of target electrons is taken into account by the use of the nonrelativistic and relativistic hydrogenic models and the Hartree–Fock–Roothaan and the relativistic Hartree–Fock–Roothaan methods. The obtained subshell ionization cross sections are compared with the experimental data and other theoretical calculations. The electronic relativistic effect and the wave‐function effect on N‐shell ionization cross sections are discussed.     

Synthesis of Al–Cr decagonal quasicrystal nanoparticles and their temperature of phase transformation to stable crystal phase

The synthesis of Al–Cr single quasicrystal (QC) nanoparticles of the decagonal phase was achieved by introducing an advanced gas flow evaporation method. By obtaining successive electron diffraction patterns for single-QC nanoparticles, the phase transformation temperature of a single-QC nanoparticle was determined to be 700 °C. It was also determined that part of the QC nanoparticle decomposed into hex-Al₈Cr₅ and Al during the phase transformation. Since the grain growth did not occur during the phase transformation in the present experiment, the inherent phase transformation temperature could be measured.     

NMR and DFT studies on persistent carbocations derived from benzo[kl]xanthene,dibenzo[d,d′]benzo[1,2‐b:4,3‐b′]difuran,and dibenzo[d,d′]benzo[1,2‐b:4,5‐b′]difuran in superacidic media

Persistent carbocations generated by the protonation of hetero‐polycyclic aromatic compounds with oxygen atom(s) were studied by experimental NMR and density function theory calculations. Benzo[kl]xanthene ( 1 ), dibenzo[d,d′]benzo[1,2‐b:4,3‐b′]difuran ( 2 ), and dibenzo[d,d′]benzo[1,2‐b:4,5‐b′]difuran ( 3 ) were synthesized by the annulation of arenediazonium salts. Compound 1 in FSO₃H‐SbF₅ (4:1)/SO₂ClF and 3 in FSO₃H‐SbF₅ (1:1)/SO₂ClF ionized to 1aH⁺ with protonation at C(4) and to 3aH⁺ with protonation at C(6), and these cations were successfully observed by NMR at low temperatures. The density function theory calculations indicated that 1aH⁺ and 3aH⁺ were the most stable protonated carbocations and that 2 should ionize to 2aH⁺ with protonation at C(6). According to the changes in ¹³C chemical shifts (Δδ¹³C), the positive charge was delocalized into the naphthalene unit for 1aH⁺ , into one benzo[b,d]furan unit for 2aH⁺ , and into one benzo[b,d]furan unit for 3aH⁺ . Copyright © 2015 John Wiley & Sons, Ltd.     

Computer-generated holograms for 3D display（ Invited Paper）

We have been studying various types of computer-generated holograms for three-dimensional （3D） displays both for a real-time holographic video display and a hard copy, or a printed hologram. For the hard copy output, we have developed a direct fringe printer, which is achieved to print over 100 gigapixels computer-generated hologram with 0.44μm pitch. In this paper, we introduce our recent progresses on the rainbow hologram, the cylindrical holograms, and the disk hologram for 3D display.