Temporal relaxation of nonequilibrium in Y-Ba-Cu-O measured from transient photoimpedance response

Abstract

Nonequilibrium in Y-Ba-Cu-0 thin films biased with a dc current is photoinduced by exposure to 300-fsec 2-eV laser pulses. The photoinduced nonequilibrium transients were measured in the superconducting, transition, and normal states occurring between 7 and 200 K. The photoabsorption produced temporal changes in the sample's impedance, which manifest themselves as transient voltage signals occurring across the samples during the nonequilibrium s relaxation process. At and above T"the observed photoresponse is thermal. Below T"aquantum response is obtained corresponding to changes in the Cooper-pair populations. In the zero-resistance superconducting state, a positive signal corresponds to quasiparticle generation and a negative signal corresponds to quasiparticle recombination.

Ultrafast linear kinetic inductive photoresponse of YBa2Cu3O7−δ meander-line structures by photoimpedance measurements

“…The interaction of light with superconducting samples is long known to perturb superconductivity [1][2][3][4] , which can be used as a probing mechanism for optoelectronic applications [5][6][7][8][9][10][11][12][13] . In general, photons of energy greater than the Cooper pair binding energy (2∆) can initiate a chain of pair-breaking events resulting in a deviation of the quasiparticle and pair densities from their equilibrium values.…”

“…In general, photons of energy greater than the Cooper pair binding energy (2∆) can initiate a chain of pair-breaking events resulting in a deviation of the quasiparticle and pair densities from their equilibrium values. Typically, these distributions depend on temperature, optical power and wavelength, thermal boundary conditions, and material properties such as electron-electron and electron-phonon interactions times, electron density, coherence length, penetration depth, and geometry 6,14 . While determining the spatial and temporal distribution of quasiparticles and pairs under a time-varying optical illumination is a profound problem in non-equilibrium superconductivity, many of the important concepts of such an interaction for device applications can be captured by means of a much simpler and more phenomenological approach, namely the kinetic inductance model 13 .…”

“…Many researchers have experimentally studied the kinetic inductive photoresponse of superconducting thin films through photoimpedance measurements 6,15 . In photoimpedance measurements, light induced changes in the microwave impedance of the superconducting structure are measured by an external high-frequency circuit.…”

Time-Resolved Photoresponse Measurements of the Electrical Conductivity of the Quasi-Two-Dimensional Organic Superconductor β-(BEDT-TTF)2I3 Using a Nanosecond Laser Pulse

“…21,35,36 Thus, photoactivation of flux creep and flux motion may be considered as the origin of the observed photoinduced increase in resistance. Other explanations considering the photoinduced creation of a pair of vortices 37 or the change of the impedance of superconducting materials caused by the modulation of the Cooper pair density 38 may also have to be considered. Temperature Dependence of Photoresponse Intensity.…”

Layered ferromagnet/superconductor heterostructures: Nonequilibrium quasiparticle dynamics and photodetector applications

“…7 Under optical irradiation, the kinetic inductance L kin of a superconducting sample is determined by the nonequilibrium energy distribution function of QPs f͑͒ and by the value of ⌬ and is given as…”