The effective surface resistance of superconductor/dielectric/metal structures

Silva, Enrico; Lanucara, Marco; Marcon, R.

doi:10.1088/0953-2048/9/11/003

Cited by 73 publications

(54 citation statements)

References 14 publications

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“…The field induced change in the intrinsic thin film impedance, ∆R ′ s + i∆X ′ s = (∆ρ 1 + i∆ρ 2 )/d, was measured for T > 60 K and µ 0 H < 0.8 T by means of a sapphire dielectric resonator operating in the TE 011 mode at 47.7 GHz. 10 The STO substrate resonances 11,12 were removed with the introduction of an additional spacer to change the substrate impedance. 13 Here, ρ 1 + iρ 2 is the complex resistivity of the film.…”

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confidence: 99%

Strong reduction of field-dependent microwave surface resistance in YBa2Cu3O7−δ with submicrometric BaZrO3 inclusions

et al. 2007

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We observe a strong reduction of the field induced thin film surface resistance measured at high microwave frequency (ν =47.7 GHz) in YBa2Cu3O 7−δ thin films grown on SrTiO3 substrates, as a consequence of the introduction of sub-micrometric BaZrO3 particles. The field increase of the surface resistance is smaller by a factor of ∼3 in the film with BaZrO3 inclusions, while the zerofield properties are not much affected. Combining surface resistance and surface reactance data we conclude (a) that BaZrO3 inclusions determine very deep and steep pinning wells and (b) that the pinning changes nature with respect to the pure film.Increasing pinning of vortex lines is an essential achievement for useful applications of superconductors in general, and of cuprate superconductors in particular due to the wide range of the H − T phase diagram where vortices are free or nearly free to move. Columnar defects are best suited to this aim, 1 but the introduction of such defects requires rather sophisticated techniques which are not suitable for mass production. Recently it was shown 2 that inclusions of BaZrO 3 (BZO) particles of dimensions in the 10-1000 nm range could determine a significant improvement of the dc properties of YBa 2 Cu 3 O 7−δ (YBCO) thin films. In particular, the critical current density 2,3 could be raised up to values useful for large scale dc applications, and the irreversibility line could be shifted above 10 T at 77 K. 4 A major interest comes from the easy incorporation of such sub-µm particles directly into the targets used for film deposition, thus making feasible the mass growth of very low losses superconductors. Pinning of vortices at high frequencies is desirable not only for devices operating in dc magnetic fields, but also because power handling is limited by depinning of selfnucleated vortices. In fact, tailored profiles of columnar defects have been shown to largely extend the linear regime at low microwave frequencies. 5 However, when the operating frequency increases, the dissipation due to oscillating vortices becomes increasingly difficult to reduce: with increasing frequency the amplitude of the vortex oscillation decreases, and becomes so small that only interactions between single vortices and pinning centers determine the response. In this regime the steepness of the pinning wells affects the balance between the reactive (elastic) and resistive (viscous) response, and the depth affects the creep of vortices. Even columnar defects, when the driving current oscillates in the high microwave range, determine at most a reduction of the dissipation of only ∼15%, as seen from measurements at * corresponding author. e-mail: silva@fis.uniroma3.it ∼50 GHz, 6 while in some cases the microwave dissipation raised after heavy-ion irradiation. 7 It seems reasonable to state that, up to now, no known artificial pinning centers have shown a significant reduction of the dissipation at very high frequencies. Measuring the response at the high edge of the microwave spectrum is a very stringent test for ...

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confidence: 99%

Strong reduction of field-dependent microwave surface resistance in YBa2Cu3O7−δ with submicrometric BaZrO3 inclusions

et al. 2007

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“…A moderate magnetic field, aligned with the c axis, is swept at each temperature from 0 to Bxm 0 HZ0.8 T (we expect that the approximate equality between applied and internal field can be inaccurate at very low fields only). In the temperature range here explored, TO70 K, the thin-film approximation is justified [10] and measurements of the field-induced shifts of Q factor and n 0 yield the field-induced variations of the complex resistivity, DrðBÞ, at fixed temperatures. The determination of DrðBÞ requires only the knowledge of geometrical factors; absolute values ofr require the cavity calibration.…”

Section: Methodsmentioning

confidence: 96%

Mixed state microwave resistivity of cuprate superconductors

Pompeo¹,

Muzzi²,

Sarti³

et al. 2006

Journal of Physics and Chemistry of Solids

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We present a compared experimental investigation of the (a, b) plane vortex-state complex resistivity at 48 GHz in YBa2Cu3O7-delta, SmBa2Cu3O7-delta and Bi2Sr2CaCu2O8+x, In YBa2Cu3O7-delta and SmBa2Cu3O7-delta the field dependence of the response can be consistently by contrast, described by a combination of flux flow and strong pair breaking due to the presence of lines of nodes in the gap. In Bi2Sr2CaCu2O8+x the data might be described by the pair breaking alone. (c) 2005 Elsevier Ltd. All rights reserved

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“…In Equation (1) G is a calculated geometrical factor, d is the film thickness, B µ 0 H is the flux density, and we have made use of the thin-film expression [17]. Complications arising from the strong temperature dependence of the substrate permittivity were dealt with according to the method described in [18].…”

Section: Methodsmentioning

confidence: 99%