Irradiation-induced disorder in high-T-c cuprates: electronic band structure study

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Spatially resolved photoluminescence spectra of thin GaAs quantum wells are measured by near-field spectroscopy, and two-energy autocorrelation functions of the spectra are derived. We demonstrate distinctly different autocorrelation functions for a 3-nm-thick quantum well grown on a (311)A surface and for quantum wells grown on (100) substrates. The autocorrelation spectra of the (311)A GaAs quantum well are quantitatively described by a statistical disorder model with a single correlation length of 17 nm

We present a theoretical model of the time-resolved excitonic photoluminescence in quantum wires. We study the role of disorder and of the exciton-free-carrier interaction on the temperature dependence of the photoluminescence lifetime. We find that at low temperature the exciton population is not thermalized in disordered quantum wires and that the lifetime is mainly determined by the localization length of the exciton. However, for large localization lengths or high enough temperatures the exciton populat

High-resolution angle-resolved photoemission data show that a metal-insulator Mott transition occurs at the surface of the quasi-two-dimensional compound 1T-TaSe2. The transition is driven by the narrowing of the Ta 5d band induced by a temperature-dependent modulation of the atomic positions. A dynamical mean-field theory calculation of the spectral function of the half-filled Hubbard model captures the main qualitative feature of the data, namely, the rapid transfer of spectral weight from the observed qu

The index n of the voltage-current characteristic of large superconductors is a crucial parameter to assess the allowed range for coil operation. In the tests of the Insert coils at the CSMC as well as in the short sample test in the SULTAN facility, it is observed that the index n dramatically decreases from the Nb3Sn strands extracted from cable-in-conduit provide the evidence of a permanent performance drop in the strands, likely due to the transverse load accumulation at the strand crossovers in the cab

We present the results of a study of the dynamics of trions and excitons in a CdTe modulationdoped quantum well as a function of temperature in the low-density regime. Using three-pulse four-wave mixing technique, we show that, at low temperature, these quasi-particles are inhomo-geneously broadened and localized due to disorder effects. At higher temperatures, trions and excitons are mobile and their homogeneous broadening is largely increased as a result of acoustic phonon scattering. Consistently, time-r

The Forschungszentrum Karlsruhe (FZK) and the Centre de Recherches en Physique des Plasmas (CRPP) are working on a joint development program to construct and test a 70 kA current lead using High Temperature Superconductors (HTS) for the Toroidal Field (TF) coil system of the International Thermonuclear Experimental Reactor, ITER-FEAT. This program follows the development program of an HTS current lead in the 20 kA range which was successfully completed in 2000. The HTS part of the current lead will be manuf

We discuss our systematic series of experiments on the photoelectric detection of the Fermi edge using a cylindrical mirror analyser on films of high-T-c oxides. grown in situ by pulsed laser ablation. The Fermi edge (comparable to the edge of the reference Ag) is very easily observed even in the two-phase BSCCO-2212 film that exhibits onsets of superconducting transitions, at 85 and 45 K. In contrast, the Fermi edge is weaker and more difficult to observe even in the state-of-the-art. highly epitaxial, mon

Disorder has a strong influence on the spectral properties of the Bi2Sr2CaCu2O8+x high-T-c superconductor, both in the normal and in the superconducting state. High-resolution photoemission reveals a progressive quasiparticle suppression with increasing disorder in electron-irradiated optimally doped single crystals. The spectral Line shapes of the disordered samples show striking analogies with those of underdoped samples specifically the widely discussed pseudogap at the chemical potential. Disorder provi

Nickel-aluminium intermetallics constitute interesting systems for the study of irradiation-induced phase transformations (order → disorder, amorphization) and production of defects. Irradiation of ordered intermetallics may induce disorder or amorphization depending on the projectile characteristics, irradiation conditions and chemical and physical properties of the target. The behavior of the various intermetallic compounds of the nickel-aluminium system with respect to electron and ion irradiation has be

Irradiation-induced embrittlement of a 2.25CrlMo is investigated by means of small punch testing and scanning electron microscopy (SEM). The ductile-brittle transition temperature (DBTT) determined by the small punch test is much lower than that determined by the standard Charpy test. There are some irradiation-induced embrittlement effects after the steel is irradiated at about 270 degrees C for 46 days with a neutron dose rate of 1.05 x 10(-8) dpa s(-1) and at about 400 degrees C for 86 days with a neutro

Segregation of P and Mo to prior austenite grain boundaries in a 2.25Cr1Mo steel subjected to neutron irradiation and ageing is examined using field emission gull scanning transmission electron microscopy (FEGSTEM) with energy dispersive X-ray microanalysis. The steel samples are irradiated and aged at around 270 and 400 degrees C, respectively. The irradiation dose rate and dose are about 1.05 x 10(-8) dpa s(-1) and 0.032 dpa for 370 degrees C-irradiation, and 1.75 x 10(-8) dpa s(-1) and 0.13 dpa for 400 d

We report on carrier-induced effects on emission and absorption in forward biased GaAs/AlGaAs V-groove quantum wire (QWR) diodes observed using low-temperature (10 K) photoluminescence (PL), electroluminescence (EL) and PL excitation (PLE) spectroscopy. In the case of simultaneous electron-hole injection we observe a band-gap renormalization (BGR) of at least 5 meV for a carrier density of approximate to 10(6) cm(-1), by comparing high-density EL spectra with low-density PLE spectra. In the case of electron

Irradiation-induced disorder in high-T-c cuprates: electronic band structure study

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Near-field autocorrelation spectroscopy of disordered semiconductor quantum wells

Modeling the photoluminescence lifetime in realistic quantum wires

Spectroscopic signatures of a bandwidth-controlled Mott transition at the surface of 1T-TaSe2

The voltage/current characteristic (n index) of the cable-in-conduit conductors for fusion

Trions and excitons in CdTe quantum wells: Lifetimes, coherence, diffusion and localization

Development of high temperature superconductor current leads for 70 kA

On detection of the Fermi edge in in situ grown thin films of high-T-c oxides

Alternative pseudogap scenario: Spectroscopic analogies between underdoped and disordered Bi2Sr2CaCu2O8+x

The order-disorder transformation and microstructure evolution in nickel-aluminium intermetallics after heavy-ion irradiation

Irradiation-induced embrittlement of a 2.25Cr1Mo steel

Grain boundary phosphorus and molybdenum segregation under irradiation and thermal conditions in a 2.25CrlMo steel

Carrier-induced effects on absorption and emission in V-groove quantum wire diodes