Intermodulation distortion measurements of MgB<sub>2</sub> thin films grown by HPCVD

Cifariello, G.; Aurino, Mario; Gennaro, Emiliano Di; Lamura, G.; Orgiani, P.; Villégier, J.C.; Xi, X. X.; Andreone, A.

doi:10.1088/1742-6596/43/1/172

Cited by 3 publications

(3 citation statements)

References 16 publications

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“…The NLME has been experimentally confirmed by IMD power measurements in high-quality YBa 2 Y 3 O 7−␦ ͑YBCO͒ films, specifically, by observation of the characteristic low-temperature divergence of the IMD power P IMD ͑T → 0 K͒ϳT −2 . [4][5][6][7] This low-temperature IMD power divergence agrees with the predictions of both DS and AO theories. Notwithstanding this agreement, the DS and AO theories are qualitatively distinct.…”

Section: Introductionsupporting

confidence: 85%

Nonlinear Meissner effect in a high-temperature superconductor: Local versus nonlocal electrodynamics

et al. 2008

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Measured intermodulation distortion ͑IMD͒ power at 1.5 GHz in a series of YBa 2 Y 3 O 7−␦ stripline resonators of varying strip widths is compared to the predictions of two qualitatively distinct theories of the nonlinear Meissner effect. The stripline resonators are patterned from a single wafer to ensure uniformity of the material properties. According to the first theory ͓T. Dahm and D. J. Scalapino, Phys. Rev. B 60, 13125 ͑1999͔͒, the IMD power is dominated by contributions from the strip edges, while according to the second theory ͓D. Agassi and D. E. Oates, Phys. Rev. B 72, 014538 ͑2005͔͒ it is dominated by contributions from the body of the strip. The parameter-free comparison of the measured data with the theoretical predictions clearly favors the latter theory. We conclude that the nonlinear component of the penetration depth must be treated with nonlocal electrodynamics. The origins of this outcome are discussed briefly in the framework of a Green's-function approach.

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Section: Introductionsupporting

confidence: 85%

Nonlinear Meissner effect in a high-temperature superconductor: Local versus nonlocal electrodynamics

et al. 2008

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“…The divergence at low T and the high sensitivity of the measurement technique constitute the advantages of the IMD as a probe for nodal lines in the gap. This methodology has been successfully applied to YBCO, where the IMD power has been experimentally observed to follow the theoretically predicted characteristic T −2 divergence at low temperatures, 3,4,[7][8][9] and leads to the conclusion that YBCO exhibits an energy gap with nodal lines.…”

Section: Introductionmentioning

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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“…6 that third harmonic distortion and third order intermodulation distortion ͑IMD͒ are in fact equivalent for patterned thin film superconducting devices. Many authors [7][8][9][10] report measurements of IMD on superconducting resonators made by introducing two signals, f 1 and f 2 , both inside the resonant peak and detecting mixing terms at, for example, 2f 2 Ϯ f 1 , also inside the resonant peak. The second order intermodulation terms at f 1 Ϯ f 2 are far outside the resonant peak, and do not address the issue of electrodynamic time scale raised by Oates.…”

Section: Three-tone Intermodulation Distortion Measurementmentioning

confidence: 99%

Synchronous measurement of even and odd order intermodulation distortion at the resonant frequency of a superconducting resonator

Pease

Dober

Remillard

2010

Review of Scientific Instruments

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A method has been developed that uses three input tones to measure both even and odd order intermodulation distortions (IMDs) inside the pass band of resonant devices. With this technique the surface current density of both the driving signal and the IMD tones can be quantified. Synchronous, or same frequency, measurement of both even and odd order distortions permits quantitative comparison of the respective nonlinearity currents measured within the same time scale. As an example of this technique, a superconducting resonator is used to generate even and odd order IMDs at the same frequency, resulting in physical conclusions, which are pertinent to current research in high temperature superconductors. While varying the level of only one tone, the expected slope of the IMD current versus the driving signal current for both orders is unity, but that is only observed at high temperature when the superconductor becomes very lossy. An observed smaller slope at lower temperatures gives support to the linear-nonlinear interaction model. Also, a sharp increase in the third order IMD relative to the second order IMD near T(C) gives support to a substantial nonlinear Meissner effect.

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Intermodulation distortion measurements of MgB₂ thin films grown by HPCVD

Cited by 3 publications

References 16 publications

Nonlinear Meissner effect in a high-temperature superconductor: Local versus nonlocal electrodynamics

Nonlinear Meissner effect in a high-temperature superconductor: Local versus nonlocal electrodynamics

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

Synchronous measurement of even and odd order intermodulation distortion at the resonant frequency of a superconducting resonator

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Intermodulation distortion measurements of MgB2 thin films grown by HPCVD

Cited by 3 publications

References 16 publications

Nonlinear Meissner effect in a high-temperature superconductor: Local versus nonlocal electrodynamics

Nonlinear Meissner effect in a high-temperature superconductor: Local versus nonlocal electrodynamics

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

Synchronous measurement of even and odd order intermodulation distortion at the resonant frequency of a superconducting resonator

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Intermodulation distortion measurements of MgB₂ thin films grown by HPCVD