Andreev, A. F. (1964). The thermal conductivity of the intermediate state in superconductors. Sov. Phys. JETP, 19(5), 1228–1231.
Abstract: It is shown that, owing to over-the-barrier reflection of electron excitations at the boundary of the normal and superconducting phases, a temperature drop occurs when there is a flow of heat. The additional thermal resistance of a superconductor in the intermediate state is calculated. It is shown that it increases exponentially as the temperature is lowered and does not depend on the electron mean free path.
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Kitaeva, G. K., Kornienko, V. V., Kuznetsov, K. A., Pentin, I. V., Smirnov, K. V., & Vakhtomin, Y. B. (2019). Direct detection of the idler THz radiation generated by spontaneous parametric down-conversion. Opt. Lett., 44(5), 1198–1201.
Abstract: We study parametric down-conversion (PDC) of optical laser radiation in the strongly frequency non-degenerate regime which is promising for the generation of quantum-correlated pairs of extremely different spectral ranges, the optical and the terahertz (THz) ones. The possibility to detect tenuous THz-frequency photon fluxes generated under low-gain spontaneous PDC is demonstrated using a hot electron bolometer. Then experimental dependences of the THz radiation power on the detection angle and on the pump intensity are analyzed.
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Cooper, L. N. (1956). Bound electron pairs in a degenerate fermi gas. Phys. Rev., 104(4), 1189–1190.
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Bardeen, J., Cooper, L. N., & Schrieffer, J. R. (1957). Theory of superconductivity. Phys. Rev., 108(5), 1175–1204.
Abstract: A theory of superconductivity is presented, based on the fact that the interaction between electrons resulting from virtual exchange of phonons is attractive when the energy difference between the electrons states involved is less than the phonon energy, â„<8f>ω. It is favorable to form a superconducting phase when this attractive interaction dominates the repulsive screened Coulomb interaction. The normal phase is described by the Bloch individual-particle model. The ground state of a superconductor, formed from a linear combination of normal state configurations in which electrons are virtually excited in pairs of opposite spin and momentum, is lower in energy than the normal state by amount proportional to an average (â„<8f>ω)2, consistent with the isotope effect. A mutually orthogonal set of excited states in one-to-one correspondence with those of the normal phase is obtained by specifying occupation of certain Bloch states and by using the rest to form a linear combination of virtual pair configurations. The theory yields a second-order phase transition and a Meissner effect in the form suggested by Pippard. Calculated values of specific heats and penetration depths and their temperature variation are in good agreement with experiment. There is an energy gap for individual-particle excitations which decreases from about 3.5kTc at T=0°K to zero at Tc. Tables of matrix elements of single-particle operators between the excited-state superconducting wave functions, useful for perturbation expansions and calculations of transition probabilities, are given.
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Gershenzon, E., Goltsman, G., Orlov, L., & Ptitsina, N. (1978). Population of excited-states of small admixtures in germanium. In Izv. Akad. Nauk SSSR, Seriya Fizicheskaya (Vol. 42, pp. 1154–1159). Mezhdunarodnaya Kniga 39 Dimitrova Ul., 113095 Moscow, Russia.
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