Effect of grain boundaries on magnetic field penetration in polycrystalline superconductors

Hylton, T. L.; Beasley, M. R.

doi:10.1103/physrevb.39.9042

Cited by 130 publications

(50 citation statements)

References 7 publications

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“…The existence and behavior of weak links are well documented and are known to provide sources of RF nonlinearities, such as IMD. [36][37][38] The IMD generated in a weak link is related to the weak-link critical current I c . The smaller the I c the larger the IMD.…”

Section: A Weak Linksmentioning

confidence: 99%

Evidence for non-s-wave symmetry of theπgap inMgB2from intermodulation distortion measurements

Agassi

Oates

Moeckly³

2009

Phys. Rev. B

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We present low-temperature low-power intermodulation-distortion ͑IMD͒ measurements of high-quality MgB 2 thin films that are inconsistent with presumed s-wave symmetry of the order parameter. The measurements were carried out in a stripline resonator at approximately 2 GHz between 1.8 K and T c . The IMD arises from the nonlinear Meissner effect in which the penetration depth is dependent on the RF magnetic field. Specifically, the observed IMD vs temperature T for T Ӷ T c / 2 varies as T −2 , while for an s-wave gap symmetry in the clean limit, the low-temperature IMD decreases exponentially with decreasing temperature. We calculate the IMD from first principles for different order-parameter symmetries using a Green's function approach and compare the results with the measured data. We propose that the observed upturn in the low-temperature IMD implies an admixture of an order parameter with nodal lines into the energy gaps of MgB 2 . Most likely, this admixture is prominent for the gap. Within the constraints of the hexagonal crystal symmetry of MgB 2 , the best fit with our IMD measurements is obtained with a gap ⌬͑ , T͒ = ⌬ 0 ͑T͒sin͑6͒, where is the azimuthal angle in the ab plane, and ⌬ 0 ͑T͒ is the amplitude, weakly temperature dependent at low temperatures. This gap symmetry entails six nodal lines. We also present low-temperature penetration-depth measurements that are consistent with the proposed nodal gap symmetry. To relate our proposition with existing literature, we review other low-temperature probes of the order-parameter symmetry. The literature presents conflicting results, some of which are in direct support of the symmetry proposed here.

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Section: A Weak Linksmentioning

confidence: 99%

Evidence for non-s-wave symmetry of theπgap inMgB2from intermodulation distortion measurements

Agassi

Oates

Moeckly³

2009

Phys. Rev. B

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“…With larger and larger misalignment angle, the nature of vortices changes from standard Abrikosov vortices to the socalled Abrikosov-Josephson (AJ) vortices, and finally to core-less Josephson vortices [13]. Many models have been developed in order to capture the GB behaviour in the microwave regimes [14][15][16][17]. Independently from the adopted model, the main signature of GB in the in-field microwave surface impedance consists in an abrupt, quasi-step-like increase of the surface resistance R s with increasing field, followed by a flat plateau [14,18].…”

Section: Experimental Technique and Data Analysismentioning

confidence: 99%

Microwave properties of DyBCO monodomain in the mixed state and comparison with other RE-BCO systems

Pompeo

Rogai

Ausloos

et al. 2011

Physica C: Superconductivity and its Applications

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“…1 In order to verify this idea and to investigate it in detail, it was suggested [2][3][4][5][6] to use HTS microstrip resonators with one large weak link formed by an artificial grain boundary ͑GB͒ extending over the entire width of the microstrip. Such a long Josephson junction ͑LJJ͒ is located in the middle of a linear resonator, so that the main mode of the resonator has the maximum amplitude of the oscillating current where the LJJ is placed.…”

Section: Introductionmentioning

confidence: 99%

Long Josephson junction embedded into a planar resonator at microwave frequencies: Numerical simulation of fluxon dynamics

Goldobin

Клушин

Siegel

et al. 2002

Journal of Applied Physics

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We have investigated numerically a system consisting of a long Josephson junction embedded into a microstrip resonator. For such a configuration the Josephson vortex dynamics in the junction is driven by the oscillating currents in the resonator. We have calculated the complex impedance of the junction at the resonant frequency. The Q factor of the resonator and the change of the resonant frequency of the whole system can then be easily calculated knowing the parameters of the resonator without Josephson junction. The fluxon dynamics and the complex impedance of the junction are simulated for different values of the junction length, damping, dc bias current, and dc magnetic field. This allows us to explain the behavior of the impedance of the junction and different loss mechanisms. In particular, we predict a nonmonotonic dependence of the both real and imaginary parts of the impedance on the amplitude of the oscillating current in the resonator for some range of parameters. Our results show that such a combination of active and passive superconducting elements forms a rather interesting nonlinear physical system which might be useful for development of tunable/switchable superconducting resonators and suggests an experimental technique for detecting trapped vortices in long junctions.

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Effect of grain boundaries on magnetic field penetration in polycrystalline superconductors

Cited by 130 publications

References 7 publications

Evidence for non-s-wave symmetry of theπgap inMgB2from intermodulation distortion measurements

Evidence for non-s-wave symmetry of theπgap inMgB2from intermodulation distortion measurements

Microwave properties of DyBCO monodomain in the mixed state and comparison with other RE-BCO systems

Long Josephson junction embedded into a planar resonator at microwave frequencies: Numerical simulation of fluxon dynamics

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