Weakly coupled grain model of high-frequency losses in high <i>T</i>
                  <i>c</i> superconducting thin films

Hylton, T. L.; Kapitulnik, A.; Beasley, M. R.; Carini, John P.; Drabeck, L.; Grüner, G.

doi:10.1063/1.99976

Cited by 237 publications

(69 citation statements)

References 5 publications

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“…The similarity in the frequency dependence of R s would suggest the microwave loss mechanisms at the three dc fields are essentially the same as each others. The linear frequency dependence rules out the loss mechanisms with f 2 dependence, such as two fluid model [25], BCS theory [26] and weakly coupled grain model [1,5]. And it implies that the hysteretic losses due to pinning and nucleation of Josephson fluxons [2] may play an important role in the loss mechanism.…”

Section: Resultsmentioning

confidence: 99%

“…This nonlinearity was believed to be mainly contributed by weak links and vortex dynamics in the HTS films [1][2][3][4][5][6][7][8][9][10][11][12]. Besides, other sources of nonlinearity, such as intrinsic pairbreaking, local heating of grain boundaries and thermal switch of superconducting grains, were also introduced to explain the diverged experimental data [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

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Anomalous microwave response of high-temperature superconducting thin-film microstrip resonator in weak dc magnetic fields

Rao

Ong

Jin

et al. 1999

Physica C: Superconductivity

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We have studied an anomalous microwave (mw) response of superconducting YBa2Cu3O 7−δ (YBCO) microstrip resonators in the presence of a weak dc magnetic field, H dc . The surface resistance (Rs) and reactance (Xs) show a correlated non-monotonic behaviour as a function of H dc . Rs and Xs were found to initially decrease with elevated H dc and then increase after H dc reaches a crossover field, Hc, which is independent of the amplitude and frequency of the input mw signal within the measurements. The frequency dependence of Rs is almost linear at fixed H dc with different magnitudes (Hc). The impedance plane analysis demonstrates that rH, which is defined as the ratio of the change in Rs(H dc ) and that in Xs(H dc ), is about 0.6 at H dc Hc. The H dc dependence of the surface impedance is qualitatively independent of the orientation of H dc .

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Anomalous microwave response of high-temperature superconducting thin-film microstrip resonator in weak dc magnetic fields

Rao

Ong

Jin

et al. 1999

Physica C: Superconductivity

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“…This residual absorption strongly depends on the quality of the material and is minimal for epitaxiaI c-axis oriented fihns. Recently D. Miller et al [16] demonstrated that the spectral dependence of the residual absorption of a variety of differently prepared YBa2CuaOT-x fihns may be quantitatively described by a model proposed by Hylton et al [10]. The film is treated as network of weakly coupled superconducting grains.…”

Section: Discussionmentioning

confidence: 99%

“…The slow signal is readily identified as a bolometric response by the non -exponential decay which follows from one dimensional heat flow through the substrate to the cold finger [8]. Both types of signals show a nonlinear dependence on intensity which may be explained by the model of an effective resistively shunted Josephson junction which has the properties of a random array of junctions [9,10]. Experimental Bi2Sr2CaCu2Os fihns were was prepared on MgO substrates by excimer laser sputtering and subsequent annealing as described previously [11].…”

Section: Introductionmentioning

confidence: 99%

Far infrared response of thin film Bi2Sr2CaCu2O8 using a free electron laser

Prettl

Lengfellner

Kaminski

et al. 1992

Int J Infrared Milli Waves

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The far infrared response of granular thin-film Bi2Sr~.CaCu208 superconductor has been investigated using long (~ 5/ts) but sharply truncated free electron laser pulses in the fi'equency range between 50 cm -1 and 125cm -1. Under constant current bias, a fast response and a slow bolometric signal component could be identified in this energy range, which is below the BCS energy gap (~ 200 cm-1). Measurements of the power dependences of the signal voltages showed that both the fast and the thermal responses are consistent with the predictions of the resistively shunted Josephson junction model. 1660 Prettl and Lengfellner IntroductionThere has been considerable interest in understanding the optical and infrared response of high-To superconductors.In previous investigations of thin granular films a wide range of response times have been observed. Slow signals, with time constants in the range of microseconds to milliseconds, were identified as a bolometric response arising from heating of the film. Fast signals in the far infrared (FIR), with time constants of nanoseconds, were attributed to several non-thermal mechanisms: an optical destruction of wave function coherence [1], the depairing of vortex-antivortex pairs [2], an optically induced charge imbalance in neighbouring superconducting grains [3] or infrared radiation generated currents in Josephson junctions inherent in granular films [4,5]. A drastic variation of the response time with frequency were found in T12Ba2CalCu208 films using FIR molecular lasers pumped by TEA CO2 lasers [6]. Below a critical frequency uc ~ 100cm -1 only fast signals, with a time constant in the order of lns, were observed. In contrast, above uc a slow response of bolometric character occurred. The transition frequency uc was identified with the energy gap value at the surface of superconducting grains. Recently non-thermal processes have been questioned by an investigation of the thermal boundary resistance of YBa2CuaOT-x films and their substrate materials [7]. It was shown that a bolometric response may occur on a nanosecond time scale: thus thermal and nonthermal effects cannot be distinguished by the time constant alone.In the present paper we report on measurements of the FIR response of thin granular film Bi2Sr2CaCu2Os using the University of California, Santa Barbara,(UCSB) Free Electron Laser (FEL). The sample was irradiated by long laser pulses truncated at the trailing edge by a rapid optical switch. Our results demonstrate that in the FIR both fast and slow signals of very different time constants are present at high powers, indicating two distinct signal generation mechanisms. The slow signal is readily identified as a bolometric response by the non -exponential decay which follows from one dimensional heat flow through the substrate to the cold finger [8]. Both types of signals show a nonlinear dependence on intensity which may be explained by the model of an effective resistively shunted Josephson junction which has the properties of a random array of junctions [9,...

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“…Such data have provided early but strong evidence against the extension to niobium films of weak link models [7][8][9] such as those which describe granular high T c cuprates [18]. Here we concentrate on a set of measurements [12] obtained with krypton as discharge gas and using electropolished copper substrates.…”

Section: Film Residual Resistances: the State Of The Artmentioning

confidence: 99%

Superconducting niobium cavities, a case for the film technology

Arbet-Engels

Benvenuti

Calatroni

et al. 2001

Nuclear Instruments and Methods in Physics Research Section A:

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Evidence is presented for niobium film cavities performing as well as niobium bulk cavities, at variance with a widespread belief that their much smaller grain size should be a fundamental limitation preventing high quality factors to be maintained over a wide range of accelerating fields. By comparing the relative merits of the bulk and film technologies, a strong case is presented in favour of the latter.

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Weakly coupled grain model of high-frequency losses in high T c superconducting thin films

Cited by 237 publications

References 5 publications

Anomalous microwave response of high-temperature superconducting thin-film microstrip resonator in weak dc magnetic fields

Anomalous microwave response of high-temperature superconducting thin-film microstrip resonator in weak dc magnetic fields

Far infrared response of thin film Bi2Sr2CaCu2O8 using a free electron laser

Superconducting niobium cavities, a case for the film technology

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