“Double superconducting transition” in YBCO thin films

Festin, Örjan; Svedlindh, Peter; Ivanov, Z. G.

doi:10.1016/s0921-4534(01)01262-x

Cited by 4 publications

(5 citation statements)

References 10 publications

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“…The only plausible explanation for the multi-step characteristics of the superconducting transition is that there exists different macroscopic regions in each film exhibiting small differences with respect to composition, 24 causing different transition temperatures as well as a widening of the superconducting transition. It is also possible that grain boundaries in the film degrade with time, causing poor superconducting connections between grains, and in the end a non-percolative superconducting system.…”

Section: Resultsmentioning

confidence: 99%

Flux noise in MgB 2 films

Festin¹,

Svedlindh²,

Kang³

et al. 2003

SPIE Proceedings

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We have performed flux noise and AC-susceptibility measurements on two 400 nm thick MgB 2 films. Both measurement techniques give information about the vortex dynamics in the sample, and hence the superconducting transition, and can be linked to each other through the fluctuation-dissipation-theorem. The transition widths for the two films are 0.3 and 0.8 K, respectively, and the transitions show a multi step-like behavior in the AC-susceptibility measurements. The same phenomenon is observed in the flux noise measurements through a change in the frequency dependence of the spectral density at each step in the transition. The results are discussed and interpreted in terms of vortices carrying an arbitrary fraction of a flux quantum as well as in terms of different macroscopic regions in the films having slightly different compositions, and hence, different critical temperatures.

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Section: Resultsmentioning

confidence: 99%

Flux noise in MgB 2 films

Festin¹,

Svedlindh²,

Kang³

et al. 2003

SPIE Proceedings

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“…The present investigation is inspired by the recent experimental results obtained by Festin et al [6] for a 1500Å thin YBCO film: A very striking double peak structure in Re[ωσ(ω)] is found; two rapid drops of Im[−ωσ(ω)] at different T are observed. The data by Festin et al are reproduced in Figs.…”

mentioning

confidence: 76%

“…One possible reason for the phase separation may lie in a combination of an inhomogeneous surface with a more homogeneous part closer to the substrate. This can lead to different oxygen contents in the two parts, which in turn results in slightly different lattice parameters causing a physical boundary between the two parts [6,[12][13][14] A further consistency check on the scenario in terms of two coupled 2D superconducting parts comes from the peak ratio defined as the ratio Re[ωσ(ω)]/Im[−ωσ(ω)] taken at the dissipation peak maxima for a given ω. For a 2D superconductor this peak ratio should vary between 2/π ≈ 0.63 for small ω to 1 for larger ω [15].…”

Section: And the Simulations Inmentioning

confidence: 99%

“…Horizontal lines shows respective zero levels for transitions and vertical lines indicates the heights of the rapid drop of Im[−ωσ(ω)] which gives a rough measure of the superconducting electrons involved. The data are taken from Ref [6]…”

mentioning

confidence: 99%

“…Figure 2.Re[ωσ(ω)] vs T measured for a thin YBCO film at the same frequencies as Im[−ωσ(ω)] in Fig.1.The inset illustrates the peak ratio defined as the ratio Re[ωσ(ω)]/Im[−ωσ(ω)] taken at the dissipation peak maxima for a given ω. The data are taken from Ref [6]…”

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confidence: 99%

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Splitting of the superconducting transition in the two weakly coupled 2D XY models

Medvedyeva¹,

Kim²,

Minnhagen³

2002

Physica C: Superconductivity

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The frequency ω and temperature T dependent complex conductivity σ of two weakly coupled 2D XY models subject to the RSJ dynamics is studied through computer simulations. A double dissipation-peak structure in Re[ωσ] is found as a function of T for a fixed frequency. The characteristics of this double-peak structure, as well as its frequency dependence, is investigated with respect to the difference in the critical temperatures of the two XY models, originating from their different coupling strengths. The similarity with the experimental data in Festin et al. [Physica C 369, 295 (2002)] for a thin YBCO film is pointed out and some possible implications are suggested.

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