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Uchiki, Hisao; Kobayashi, Takayoshi; Sakaki, Hiroyuki |
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Title |
Photoluminescence and energyâ€loss rates in GaAs quantum wells under highâ€density excitation |
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1987 |
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J. Appl. Phys. |
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62 |
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3 |
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1010-1016 |
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2DEG, GaAs/AlGaAs, heat flow, electron-phonon, hole-phonon, carrier-phonon, interactions |
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Abstract |
The timeâ€resolved luminescence spectra from excited conduction subbands in three samples of multiâ€quantumâ€well GaAs/AlxGa1-xAs (x=0.3 and 1) semiconductors with several well widths and barrier heights were obtained under highâ€density excitations by a 30â€ps pulsed laser at 532 nm, which generated electron–hole pairs to the concentration of 1010–1013/cm2 per well per pulse at 77 K. The temperature and the Fermi energy of electron were determined by fitting best the constructed timeâ€resolved spectrum to the observed, and the timeâ€dependent electron energy was obtained by using these parameters. The energyâ€loss rates of hot electrons are at least twice smaller than the calculated ones induced by the electronâ€polar phonon scattering, including the screening effect due to the high carrier density. |
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635 |
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Santhanam, P.; Wind, S.; Prober, D. E. |
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Title |
Localization, superconducting fluctuations, and superconductivity in thin films and narrow wires of aluminum |
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Journal Article |
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Year |
1987 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
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35 |
Issue |
7 |
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3188-3206 |
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Keywords |
Al films; electron-phonon scattering; electron-electron scattering; Disordered structures; amorphous and glassy solids, Relaxation times and mean free paths, Galvanomagnetic and other magnetotransport effects |
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We report a comprehensive set of experiments on wide and narrow thin-film strips of aluminum which test the predictions of recent localization theory. The experiments on wide films in the two-dimensional regime confirm the theoretical predictions and also yield insight into inelastic mechanisms and spin-orbit scattering rates. Our extension of the existing theory for one-dimensional systems to include spin-orbit scattering and Maki-Thompson superconducting fluctuations is verified by the experiments. We find clear evidence for one-dimensional localization, with inferred inelastic rates identical to those in two-dimensional films. The prediction of the localization theory for a dimensional crossover from two-dimensional to one-dimensional behavior is also confirmed. We have reanalyzed the results of some previous experiments on thin films and narrow wires in light of these results. |
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RPLAB @ gujma @ |
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757 |
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Gershenzon, E. M.; Gol'tsman, G. N.; Mirskii, G. I. |
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Submillimeter backward-wave-tube spectrometer-relaxometer |
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Journal Article |
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1987 |
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Pribory i Tekhnika Eksperimenta |
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Pribory i Tekhnika Eksperimenta |
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30 |
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4 |
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131-137 |
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BWO, applications |
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A backward-wave-tube (BWT) spectrometer-relaxometer is described that is designed for study of the relaxation characteristics of photoconductors in the wavelength range of 2-0.25 mm – in particular, to measure the relaxation times of the submillimeter photoconductivity of germanium in the range of 10[sup:-4]-10[sup:-9] sec and to determine from these data the concentration of compensating impurities of from 10[sup:10] to 10[sup:14] cm[sup:-3]. The instrument uses the beats of the oscillations of two BWTs and records the amplitude-frequency response of the specimen with variation of the beat frequency from 10[sup:4] to 10[sup:8] Hz with accumulation of the desired signal for less than or equal to1 sec by means of a quadrature synchronous detector. The beat frequency is stabilized and the quadrature voltages of the synchronous detector are formed by means of phase-locked loops. |
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Russian |
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1699 |
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Gershenzon, Ye. M.; Goltsman, G. N.; Yelantyev, A. I.; Petrova, Ye. B.; Ptitsina, N. G.; Filatov, V. S. |
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Title |
Lecture demonstrations of properties of superconductors and liquid helium |
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Journal Article |
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1987 |
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USSR Rept Phys. Math. JPRS UPM |
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USSR Rept Phys. Math. JPRS UPM |
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24 |
Issue |
7 |
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51 |
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demonstrations, lections |
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New demonstrations for low temperature physics courses are described. Two transparent Dewar vacuum flasks fitting one inside the other with the external flask for nitrogen and the internal flask for helium are used. The helium temperature can be regulated in the 4.2 to 1.6 K range and the effects of reducing helium to the superfluid state at 2.17 K can be shown: boiling abruptly stops and superfluid flow appears. In order to show the electric and magnetic characteristics of superconductivity, a superconducting NbTi solenoid containing nonsuperconducting wire and germanium and superconducting Nb materials with different critical temperatures is placed in the helium refrigerant vessel. The fall of the resistance at the critical temperatures can be shown. In order to show magnetic field and superconductive current flow properties a shunt of superconductive material is connected in parallel to the coil and is enclosed in a teflon container with a heater which can vary its temperature. When it is heated and not superconductive, magnetic field effects can be demonstrated and when it is unheated and superconducting a continuous current can be demonstrated. |
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1704 |
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Gol'tsman, G. N.; Gusinskii, E. N.; Malyavkin, A. V.; Ptitsina, N. G.; Selevko, A. G.; Edel'shtein, V. M. |
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Title |
The excitonic Zeeman effect in uniaxially-strained germanium |
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Journal Article |
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1987 |
Publication |
Sov. Phys. JETP |
Abbreviated Journal |
Sov. Phys. JETP |
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Volume |
65 |
Issue |
6 |
Pages |
1233-1241 |
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Keywords |
Ge, Zeeman effect |
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We have carried out a high-resolution spectroscopic study of the absorption of submillimeter radiation by free excitons in germanium compressed along the [ 1 11 ] axis in a magnetic field parallel to the compression axis. In particular, we studied the splitting of the 1s- 2p transition in fields up to 6 kOe at T = 1.6 K, and observed a complex pattern in the Zeeman splitting which we believe is related to the effect of thermal motion of the excitons in a magnetic field on their internal structure (the magneto-Stark effect). The calculated submillimeter spectrum of excitons agrees with the experimental data. We predict that in a magnetic field the energy of the 2p, term is a minimum at a finite value of the exciton momentum perpendicular to the field-that is, the energy minimum forms a ring in momentum space. It follows that the density of states for this term must be a nonmonotonic function of the energy. A theory is developed of analogous phenomena in positronium. |
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1705 |
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