Heslinga, D. R., Shafranjuk, S. E., van Kempen, H., & Klapwijk, T. M. (1994). Observation of double-gap-edge Andreev reflection at Si/Nb interfaces by point-contact spectroscopy. Phys. Rev. B, 49(15), 10484–10494.
Abstract: Andreev reflection point-contact spectroscopy is performed on a bilayer consisting of 50-nm degenerately doped Si backed with Nb. Due to the short mean free path both injection into and transport across the Si layer are diffusive, in contrast to the ballistic conditions prevailing in clean metal layers. Nevertheless a large Andreev signal is observed in the point-contact characteristics, not reduced by elastic scattering in the Si layer or by interface scattering, but only limited by the transmission coefficient of the metal-semiconductor point contact. Two peaks in the Andreev reflection probability are visible, marking the values of the superconducting energy gap at the interface on the Nb and Si sides. This interpretation is supported by a method of solving the Bogolubov equations analytically using a simplified expression for the variation of the order parameter close to the interface. This observation enables a comparison with theoretical predictions of the gap discontinuity in the proximity effect. It is found that the widely used de Gennes model does not agree with the experimental data.
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Sergeev, A. V., Semenov, A. D., Kouminov, P., Trifonov, V., Goghidze, I. G., Karasik, B. S., et al. (1994). Transparency of a YBa2Cu3O7-film/substrate interface for thermal phonons measured by means of voltage response to radiation. Phys. Rev. B Condens. Matter., 49(13), 9091–9096.
Abstract: The transparency of a film/substrate interface for thermal phonons was investigated for YBa2Cu3O7 thin films deposited on MgO, Al2O3, LaAlO3, NdGaO3, and ZrO2 substrates. Both voltage response to pulsed-visible and to continuously modulated far-infrared radiation show two regimes of heat escape from the film to the substrate. That one dominated by the thermal boundary resistance at the film/substrate interface provides an initial exponential decay of the response. The other one prevailing at longer times or smaller modulation frequencies causes much slower decay and is governed by phonon diffusion in the substrate. The transparency of the boundary for phonons incident from the film on the substrate and also from the substrate on the film was determined separately from the characteristic time of the exponential decay and from the time at which one regime was changed to the other. Taking into account the specific heat of optical phonons and the temperature dependence of the group velocity of acoustic phonons, we show that the body of experimental data agrees with acoustic mismatch theory rather than with the model that assumes strong diffusive scattering of phonons at the interface.
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Matsushima, F., Odashima, H., Iwasaki, T., Tsunekawa, S., & Takagi, K. (1994). Frequency measurement of pure rotational transitions of H2O from 0.5 to 5 THz. In Conference on precision electromagnetic measurements digest (pp. 23–24).
Abstract: Frequencies of H2O pure rotational transitions from 0.5 to 5 THz have been measured with an accuracy of one part in 109 using a tunable far-infrared spectrometer. Measured frequencies of more than a hundred spectral lines provide an excellent wavelength and frequency calibration standard for the far infrared.
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Gershenzon, E. M., Gol'tsman, G. N., Zorin, M. A., Karasik, B. S., & Trifonov, V. A. (1994). Nonequilibrium and bolometric response of YBaCuO films in a resistive state to infrared low intensity radiation. In Council on Low-temp. Phys. (pp. 82–83).
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Karasik, B. S., Milostnaya, I. I., Zorin, M. A., Elantev, A. I., Gol'tsman, G. N., & Gershenzon, E. M. (1994). Subnanosecond S-N and N-S switching of YBCO film induced by current pulse. Phys. C: Supercond., 235-240, 1981–1982.
Abstract: A transition of YBCO bridge 60 nm thick from superconducting to normal state induced by an abrupt current step has been studied. A subnanosecond stage has been observed during both S-N and N-S transition. The data obtained can be explained by hot-electron phenomena. On the basis of experimental results a prediction of picosecond switch performance has been made.
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