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Gershenzon EM, Gershenzon ME, Gol'tsman GN, Karasik BS, Semenov AD, Sergeev AV. Light-induced heating of electrons and the time of the inelastic electron-phonon scattering in the YBaCuO compound. JETP Lett. 1987;46(6):285–7.
Abstract: For the first time, measurements have been made on the electron energy relaxation time due to the electron--phonon interaction in films of the YBaCuO superconductor. The results indicate a significant intensification of the electron--phonon interaction in this compound as compared with normal superconducting metals.
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Gol'tsman GN, Gusinskii EN, Malyavkin AV, Ptitsina NG, Selevko AG, Edel'shtein VM. The excitonic Zeeman effect in uniaxially-strained germanium. Sov Phys JETP. 1987;65(6):1233–41.
Abstract: 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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Gershenzon EM, Gol'tsman GN, Karasik BS, Semenov AD. Measurement of the energy gap in the compound YBaCu3O9-δ on the basis of the IR absorption spectrum. JETP Lett. 1987;46(5):237–8.
Abstract: For the first time the long-wave infrared absorption spectrum has been measured by means of the bolometric effect and energy gap for high-temperature superconducting ceramics YBa/sub 2/Cu/sub 3/O/sub 9-delta/ has been determined from absorption threshold. 2delta/kT/sub c/ value is equal to 0.6.
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Gershenzon EM, Gol'tsman GN. Effect of electromagnetic radiation on a superconductor in a magnetic field. In: Izv. Akad. Nauk SSSR, Seriya Fizicheskaya. Vol 52.; 1988. p. 449–51.
Abstract: The effect of electromagnetic radiation on thin superconducting films of Nb with a large number of static defects is investigated experimentally for the case where the film is in the resistive state due to an applied magnetic field and transport current. The results obtained are found to be well described by a model of spatially homogeneous electron heating. It is noted that the results obtained here for Nb films are also valid for Al, NbN, and MoRe films.
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Gershenzon EM, Gol'tsman GN, Mirskii GI. Submillimeter backward-wave-tube spectrometer-relaxometer. Pribory i Tekhnika Eksperimenta. 1987;30(4):131–7.
Abstract: 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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Gershenzon EM, Gol'tsman GN, Elant'ev AI, Karasik BS, Potoskuev SE. Intense electromagnetic radiation heating of superconductor electrons in resistive state. Fizika Nizkikh Temperatur. 1988;14(7):753–63.
Abstract: An experimental study is made of the effect of intense radiation in the millimeter and submillimeter ranges on thin and narrow Nb films in the resistive state. It is found that the excess resistance resulting from radiation and the dependence of its relaxation time on radiation intensity and transport current can be explained in terms of the effect of electron heating. Quantitative agreement is obtained between the experimental data and a homogeneous electron heating model.
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Aksaev EE, Gershenzon EM, Gol'tsman GN, Semenov AD, Sergeev AV. Interaction of electrons with thermal phonons in YBa2Cu3O7-δ films at low temperatures. JETP Lett. 1989;50(5):283–6.
Abstract: The time of electron-phonon interaction tau(eph) in YBaCuO films at low temperatures is studied. This is measured as the time of resistance relaxation in the resistive state of the superconducter, and is also determined from the increase in resistance under the action of radiation. Consistent results of these methods show that resistance relaxation in the resistive state is caused by cooling of the electron subsystem with respect to the phonon subsystem. The time tau(eph) is found to be inversely proportional to the temperature and comes to 80 ps when T = 1.6 K and 5 ps when T = 30 K. 6 refs.
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Varyukhin SV, Zakharov AA, Gershenzon EM, Gol'tsman GN, Ptitsina NG, Chulkova GM. Low energy excitation in La2CuO4. Sverkhprovodimost': Fizika, Khimiya, Tekhnika. 1990;3(5):832–7.
Abstract: 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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Gershenzon EM, Gol'tsman GN, Potapov VD, Sergeev AV. Restriction of microwave enhancement of superconductivity in impure superconductors due to electron-electron interaction. Solid State Communications. 1990;75(8):639–41.
Abstract: Transition from microwave enhancement of supercurrent to superconductivity suppression is investigated in impure superconductors. It is demonstrated that the frequency range of the enhancement effect narrows with the decrease of the electron mean free path, l, and at l ⩽ 1 nm electron heating is observed in the whole frequency range. Dependences of frequency boundaries on l are explained by taking into account strong electron-electron interaction in impure metals.
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Varyukhin SV, Zakharov AA, Gershenzon EM, Gol'tsman GN, Ptitsyna NG, Chulkova GM. AC losses and submillimeter absorption in single crystals La2CuO4. Phys B Condens Mat. 1990;165-166:1269–70.
Abstract: The La2CuO4 single crystals were used to carry out the measurements of transmission spectra within the submillimeter range of wavelengths, as well as the capacitance C and conductivity G in the region of acoustic frequencies of the metal-dielectric-La2Cu04 system at low temperatures. The optical spectra display a threshold character. There takes place a sharp decreasing of transmission signal in the energy range of hυ>1.5meV. The C(ω,T) and G(ω,T) dependences have a universal form characteristic of relaxation processes of the Debye type. The relaxation time dependence displays a thermoactivation character τ(T)-exp(ξ/T) with a gap value of ξ≃2meV,coinciding with the optical one. It is assumed that there exist excitations with a characteristic energy ~ 2meV in La2Cu04.A possible nature of the revealed low-energy excitations is discussed.
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