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Author Semenov, A. D.; Nebosis, R. S.; Gousev, Yu. P.; Heusinger, M. A.; Renk, K. F. openurl 
  Title Analysis of the nonequilibrium photoresponse of superconducting films to pulsed radiation by use of a two-temperature model Type Journal Article
  Year 1995 Publication Phys. Rev. B Abbreviated Journal Phys. Rev. B  
  Volume 52 Issue 1 Pages 581-590  
  Keywords HEB, NbN phonon scecific heat, Cp  
  Abstract Photoresponse of a superconducting film in the resistive state to pulsed radiation has been studied in the framework of a model assuming that two different effective temperatures can be assigned to the quasiparticle and phonon nonequilibrium distributions. The coupled electron-phonon-substrate system is described by a system of time-dependent energy-balance differential equations for effective temperatures. An analytical solution of the system is given and calculated voltage transients are compared with experimental photoresponse signals taking into account the radiation pulse shape and the time resolution of the readout electronics. It is supposed that a resistive state (vortices, fluxons, network of intergrain junctions, hot spots, phase slip centers) provides an ultrafast connection between electron temperature changes and changes of the film resistance and thus plays a minor role in the temporal evolution of the response. In accordance with experimental observations a two-component response was revealed from simulations. The slower component corresponds to a bolometric mechanism while the fast component is connected with the relaxation of the electron temperature. Calculated photoresponse transients are presented for different ratios of the electron and phonon specific heat, radiation pulse durations and fluences, and frequency band passes of registration electronics. From the amplitude of the bolometric component we determine the radiation energy absorbed in a film. This enables us to reveal an intrinsic electron-phonon scattering time even if it is much shorter than the time resolution of readout electronics. We analyze experimental voltage transients for NbN, YBa2Cu3O7, and TlBa2Ca2Cu3O9 superconducting films and find the electron-phonon interaction times at the transition temperatures of 17, 2.5, and 1.8 ps, respectively. The values are in reasonable agreement with data of other experiments.  
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  Call Number Serial (down) 903  
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Author Bardeen, J.; Cooper, L. N.; Schrieffer, J. R. openurl 
  Title Theory of superconductivity Type Journal Article
  Year 1957 Publication Phys. Rev. Abbreviated Journal Phys. Rev.  
  Volume 108 Issue 5 Pages 1175-1204  
  Keywords BCS  
  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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  Call Number Serial (down) 901  
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Author Bardeen, J.; Cooper, L. N.; Schrieffer, J. R. openurl 
  Title Microscopic theory of superconductivity Type Journal Article
  Year 1957 Publication Phys. Rev. Abbreviated Journal Phys. Rev.  
  Volume 106 Issue Pages 162-164  
  Keywords BCS  
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  Notes Approved no  
  Call Number Serial (down) 900  
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Author Cooper, L. N. openurl 
  Title Bound electron pairs in a degenerate fermi gas Type Journal Article
  Year 1956 Publication Phys. Rev. Abbreviated Journal Phys. Rev.  
  Volume 104 Issue 4 Pages 1189-1190  
  Keywords BCS  
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  Call Number Serial (down) 899  
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Author Vercruyssen, N.; Verhagen, T. G. A.; Flokstra, M. G.; Pekola, J. P.; Klapwijk, T. M. openurl 
  Title Evanescent states and nonequilibrium in driven superconducting nanowires Type Journal Article
  Year 2012 Publication Phys. Rev. B Abbreviated Journal Phys. Rev. B  
  Volume 85 Issue Pages 224503(1-10)  
  Keywords Al HEB, Al superconducting nanowire, global state, bimodal state, quasiclassical kinetic equations, Usadel equation  
  Abstract We study the nonlinear response of current transport in a superconducting diffusive nanowire between normal reservoirs. We demonstrate theoretically and experimentally the existence of two different superconducting states appearing when the wire is driven out of equilibrium by an applied bias, called the global and bimodal superconducting states. The different states are identified by using two-probe measurements of the wire, and measurements of the local density of states with tunneling probes. The analysis is performed within the framework of the quasiclassical kinetic equations for diffusive superconductors.  
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  Notes Approved no  
  Call Number Serial (down) 898  
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