Varyukhin, S. V., Zakharov, A. A., Gershenzon, E. M., Gol'tsman, G. N., Ptitsyna, N. G., & Chulkova, G. M. (1990). AC losses and submillimeter absorption in single crystals La2CuO4. Phys. B Condens. Mat., 165-166, 1269–1270.
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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Gol’tsman, G. N., Semenov, A. D., Sergeev, A. V., Aksaev, E. E., Gogidze, I. G., & Gershenzon, E. M. (1993). Electron-phonon interaction in thin YBaCuO films and fast detectors. In M. Meissner, & R. O. Pohl (Eds.), Phonon Scattering in Condensed Matter VII. Springer Series in Solid-State Sciences (Vol. 112, pp. 184–185).
Abstract: The thin. YBaCuO film response to laser and submillimeter radiation demonstrates the picosecond nonequilibrium peak on the nanosecond bolometric background. Experimental data give an evidence for the spectral dependence of picosecond photoresponse probably due to a poor efficiency of electron multiplication processes. Presented results prove an availability of fast YBaCuO thin film detector.
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Heusinger, M. A., Nebosis, R. S., Schatz, W., Renk, K. F., Gol’tsman, G. N., Karasik, B. S., et al. (1993). Temperature dependence of bolometric and non-bolometric photoresponse of a structured YBa2Cu3O7-δ thin film. In M. Meissner, & R. O. Pohl (Eds.), Phonon Scattering in Condensed Matter VII. Springer Series in Solid-State Sciences (Vol. 112, pp. 193–195).
Abstract: We investigated the temperature dependence of the transient voltage photoresponse of a current biased structured YBa2Cu3O7−δ thin film in its transition temperature region, around 79 K. Both, picosecond nonbolometric and nanosecond bolometric response to ultrashort far-infrared laser pulses were found for frequencies between 25 cm−1 and 215 cm−1. We will discuss optimum conditions for radiation detection and present an analysis of the dynamical behaviour of excited high T c thin films.
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Sergeev, A. V., & Livanov, D. V. (1993). Phonon renormalization of thermoelectric power of high-Tc materials. In M. Meissner, & R. O. Pohl (Eds.), Phonon Scattering in Condensed Matter VII. Springer Series in Solid-State Sciences (Vol. 112, pp. 204–205).
Abstract: Renormalization of thermoelectric power due to Nielsen — Taylor effect (interference between electron-phonon and electron- impurity interactions) is used for the explanation of the temperature dependence and sign of the thermopower in high-Tc materials. In the framework of the model the negative sign of TEP of untwinned YBa2Cu3O7−x crystal in a-direction observed by Howson et. al. is connected to the strong hole scattering via O-vacancies in chains.
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Sergeev, A. V., Aksaev, E. E., Gogidze, I. G., Gol’tsman, G. N., Semenov, A. D., & Gershenzon, E. M. (1993). Thermal boundary resistance at YBaCuO film-substrate interface. In M. Meissner, & R. O. Pohl (Eds.), Phonon Scattering in Condensed Matter VII. Springer Series in Solid-State Sciences (Vol. 112, pp. 405–406).
Abstract: The nanosecond voltage response of YBaCuo films on Al2O3, MgO and ZrO2 substrates to electromagnetic radiation of millimeter and visible ranges has been investigated. The analysis of experimental conditions for Al2O3 and MgO substrates shows that the resistance change is monitored by the Kapitza boundary shift of temperature during the temporal interval ~ 100 ns limited by the time of phonon return from a substrate into a film. The observed exponential voltage decay is described by the phonon escape time which is proportional to the film thickness and is weakly temperature dependent.
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