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Gershenzon, E. M., Gol'tsman, G. N., & Kagane, M. L. (1977). Energy spectrum of acceptors in germanium and its response to a magnetic field. Sov. Phys. JETP, 45(4), 769–776.
Abstract: We investigated the spectrum of the submillimeter photoconductivity of p-Ge at helium temperatures and the effects of a magnetic field up to 40 kOe on the spectrum. A large number of lines of transitions between the excited states of the acceptors was observed, some of the lines were identified, and the energies of a number of spectral levels B, Al, Ga, In, and TI in Ge were identified. The results are compared with calculations and with experimental data obtained from the spectra of the photoexcitation of the ground state of the impurities. Using one transition as an example, we discuss the splitting of the excited states of acceptors in the magnetic field and under uniaxial compression.
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Gershenzon, E. M., Gol'tsman, G., & Ptitsina, N. G. (1973). Energy spectrum of free excitons in germanium. JETP Lett., 18(3), 93.
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Gershenzon, E. M., Gol'tsman, G. N., & Elant'ev, A. I. (1977). Energy spectrum of the donors in GaAs and Ge and its reaction to a magnetic field. Sov. Phys. JETP, 45(3), 555–565.
Abstract: The spectrum of the submillimeter photoconductivity of n-GaAs and n-Ge in a magnetic field up to 60 kOe at helium temperatures was investigated. A large number of lines due to transitions between excited states of the donors have been investigated, and the measurement results were used to determine a number of levels of the energy spectrum in a wide range of magnetic fields. For GaAs, these data are compared with calculations of the energy spectrum of the hydrogen atom in magnetic fields up to -2X lo9 Oe. For the donors in Ge, the energy spectrum is investigated at different orientations of the magnetic field relative to the crystallographic axes (H 11 [loo], [I 1 I], [110]), and these results are also compared with the corresponding calculations.
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Beck, M., Leiderer, P., Kabanov, V. V., Gol'tsman, G., Helm, M., & Demsar, J. (2012). Energy-gap dynamics of a superconductor NbN studied by time-resolved terahertz spectroscopy. In INIS (Vol. 45, pp. 1–3).
Abstract: Using time-resolved terahertz (THz) spectroscopy we performed direct studies of the photoinduced suppression and recovery of the SC gap in a conventional SC NbN. Both processes are found to be strongly temperature and excitation density dependent. The analysis of the data with the established phenomenological Rothwarf-Taylor model enabled us to determine the important microscopic constants: the Cooper pair-breaking rate via phonon absorption and the bare quasiparticle recombination rate. From the latter we were able to extract the dimensionless electron-phonon coupling constant, λ=1.1±0.1, in excellent agreement with theoretical estimates. The technique also allowed us to determine the absorbed energy required to suppress SC, which in NbN equals the thermodynamic condensation energy (in cuprates the two differ by an order of magnitude). Finally, we present the first studies of dynamics following resonant excitation with intense narrow band THz pulses tuned to above and below the superconducting gap. These suggest an additional process, particularly pronounced near Tc, that could be attributed to amplification of SC via effective quasiparticle cooling.
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Beck, M., Klammer, M., Lang, S., Leiderer, P., Kabanov, V. V., Gol’tsman, G. N., et al. (2011). Energy-gap dynamics of superconducting NbN thin films studied by time-resolved terahertz spectroscopy. arXiv:1102.5616v2 [cond-mat.supr-con]. Retrieved June 30, 2024, from https://arxiv.org/abs/1102.5616v2
Abstract: Using time-domain Terahertz spectroscopy we performed direct studies of the photoinduced suppression and recovery of the superconducting gap in a conventional BCS superconductor NbN. Both processes are found to be strongly temperature and excitation density dependent. The analysis of the data with the established phenomenological Rothwarf-Taylor model enabled us to determine the bare quasiparticle recombination rate, the Cooper pair-breaking rate and the electron-phonon coupling constant, \lambda = 1.1 +/- 0.1, which is in excellent agreement with theoretical estimates.
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