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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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Lecture demonstrations of properties of superconductors and liquid helium |
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1987 |
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USSR Rept Phys. Math. JPRS UPM |
Abbreviated Journal |
USSR Rept Phys. Math. JPRS UPM |
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24 |
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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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Varyukhin, S. V.; Zakharov, A. A.; Gershenzon, E. M.; Gol'tsman, G. N.; Ptitsina, N. G.; Chulkova, G. M. |
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Title |
Low energy excitation in La2CuO4 |
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Journal Article |
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Year |
1990 |
Publication |
Sverkhprovodimost': Fizika, Khimiya, Tekhnika |
Abbreviated Journal |
Sverkhprovodimost': Fizika, Khimiya, Tekhnika |
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3 |
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5 |
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832-837 |
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metal-dielectric-La2CuO4, monocrystals |
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Measurements of transmission and photoconductivity spectra in submillimeter wave length range as well as of capacity C and conductivity G in the region of acoustic frequencies of metal-dielectric-La2CuO4 system at low temperatures are performed using La2CuO4 monocrystals. Optical spectra posses a threshold character, a sharp decrease of transmission and photocoductivity signal occurs in the energy region hν>1.5 MeV. C(ω,T) and G(ω, T) dependences have a universal form typical of Debye type relaxation processes. Relaxation time dependence is of thermoactivated character τ(T)∼exp(ξ/T) with the gap value ξ≅2 meV. It is assumed that excitations with characteristic energy of ∼2 meV exist in La2CuO4. A possible nature of the detected low-energy excitations is discussed. |
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1688 |
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Verevkin, A. A.; Ptitsina, N. G.; Chulcova, G. M.; Gol'tsman, G. N.; Gershenzon, E. M.; Yngvesson, K. S. |
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Direct measurements of energy relaxation time of electrons in AlGaAs/GaAs heterostructures under quasi-equilibrium conditions |
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1996 |
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Surface Science |
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Surface Science |
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361-362 |
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569-573 |
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2DEG, AlGaAs/GaAs heterostructures |
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For the first time, results are presented of a direct measurement of the energy relaxation time τε of 2D electrons in an AlGaAs/GaAs heterojunction at T = 1 and 5–20 K. A weak temperature dependence of τε for the T > 4K range and a linear temperature dependence of the reciprocal of τε for T < 4K have been observed. The linear dependence τε−1 ≈ T in the Bloch-Gruneisen regime is direct evidence of the predominance of the piezo-electric mechanism of electron-phonon interaction in non-elastic electron scattering processes. The values of τε in this regime are in very good agreement with the results of the Karpus theory. At higher temperatures, where the deformation-potential scattering becomes noticeable, a substantial disagreement between the experimental data and the theoretical results is observed. |
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0039-6028 |
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1609 |
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Gershenson, E. M.; Gol'tsman, G. N.; Elant'ev, A. I.; Kagane, M. L.; Multanovskii, V. V.; Ptitsina, N. G. |
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Title |
Use of submillimeter backward-wave tube spectroscopy in determination of the chemical nature and concentration of residual impurities in pure semiconductors |
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1983 |
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Sov. Phys. Semicond. |
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Sov. Phys. Semicond. |
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17 |
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8 |
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908-913 |
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BWO spectroscopy, pure semiconductors, residual impurities |
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Применение субмиллиметровой ЛОВ спектроскопии для определения химической природы и концентрации примесей в чистых полупроводниках |
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1714 |
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Gershenzon, E. M.; Gol'tsman, G. N.; Multanovskii, V. V.; Ptitsina, N. G. |
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Title |
Kinetics of electron and hole binding into excitons in germanium |
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1983 |
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Sov. Phys. JETP |
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Sov. Phys. JETP |
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57 |
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2 |
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369-376 |
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Keywords |
Ge, electron and hole binding |
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The kinetics of binding of free carriers'into excitons under stationary and nonstationary conditions is studied by investigating the submillimeter photoconductivity of Ge in a wide range of temperatures and of excitation levels. It is shown that the absolute values and the temperature dependence of the binding cross section (o- T-'.' ) can be satisfactorily described by the cascade recombination theory. The value of o and its temperature dependence differ significantly from the cross sections, measured in the same manner, for capture by attracting small impurities. Under nonstationary conditions, just as in the case of recombination with shallow impurities, a signifi- cant role is played by the sticking of the carriers in highly excited states. |
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1711 |
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