Magnetic field dependence of the superconducting fluctuation contribution to NMR-NQR relaxation

Mosconi, Pietro; Rigamonti, A.; Varlamov, A. A.

doi:10.1007/bf03162376

Cited by 31 publications

(17 citation statements)

References 27 publications

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“…(Heym, 1992;Kuboki and Fukuyama, 1989;Maniv and Alexander, 1977;Randeria and Varlamov, 1994), while the second term provides the magnetic field dependence first calculated in Ref. (Mosconi et al, 2000). One can see that the MT contribution dominates when the pair-breaking is weak, i.e., in weak fields SFs increase the NMR relaxation rate.…”

Section: Vicinity Of Tc0 (Domains I-iii)mentioning

confidence: 88%

“…The effect of superconducting fluctuations on the NMR relaxation rate was studied in many works (Carretta et al, 1996;Mitrović et al, 1999Mitrović et al, , 2002Eschrig et al, 1999;Gorny et al, 1999;Heym, 1992;Kuboki and Fukuyama, 1989;Maniv and Alexander, 1977;Mosconi et al, 2000;Prando et al, 2011;Randeria and Varlamov, 1994). It can be observed in a wide range of temperatures and magnetic fields beyond the second critical field line H c2 (T ) It is well-known that the density of quasiparticle excitations, which enters quadratically into the NMR relaxation rate W , is suppressed by SFs (Abrahams et al, 1970;Di Castro et al, 1990).…”

Section: A General Expression For the Fluctuation Nmr Relaxation Ratementioning

confidence: 99%

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Fluctuation spectroscopy: From Rayleigh-Jeans waves to Abrikosov vortex clusters

2018

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5 We define the FCP concentration in d-dimensional space. This means that it determines the number of pairs per volume in the 3D case, the number of pairs per unit square in the 2D case, and the number of pairs per unit length in 1D. Since both wires and films are actual objects in three dimensional space, we can approximate the 3D concentration of FCPs,Ñ (3) , byÑ (3) = N (1) /s 2 for wires, where s 2 is the wire cross-section andÑ (3) = N (2) /s for films, where s is the thickness of the film, respectively.

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Section: Vicinity Of Tc0 (Domains I-iii)mentioning

confidence: 88%

Section: A General Expression For the Fluctuation Nmr Relaxation Ratementioning

confidence: 99%

Fluctuation spectroscopy: From Rayleigh-Jeans waves to Abrikosov vortex clusters

2018

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“…While the field is a necessary tool to carry out relevant measurements, a strong field is expected to suppress the fluctuating Cooper pairs. Thus, a variety of phenomena are reflected in the dependence of the SF and of the fluctuating diamagnetism ͑FD͒ on the external field H. Moreover, experimentally studying the effect of H on SF can be quite challenging, as for the cases of the field dependence of the spin susceptibility controlling the NMR spin-lattice relaxation 2 or the diamagnetic susceptibility dia related to FD. 3 A meaningful study of the field dependence of SF can be carried out in grains of size d smaller than the coherence length , i.e., in the zero-dimensional ͑0D͒ limit.…”

Section: Introductionmentioning

confidence: 99%

Zero-dimensional superconducting fluctuations and fluctuating diamagnetism in lead nanoparticles

et al. 2006

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High-resolution superconducting quantum interference device magnetization measurements in lead nanoparticles with particle size d less than the superconducting coherence length are used to study zero-dimensional fluctuating diamagnetism. The diamagnetic magnetization M dia ͑H, T = const͒ as a function of the applied magnetic field H at constant temperature is reported in the critical region and compared with the observed behavior in the temperature range where the first-order fluctuation corrections are expected to hold. The magnetization curves are analyzed in the framework of exact fluctuation theories based on the GinzburgLandau functional for ӷ d. The role of the upturn field H up , where the slope of M dia ͑H͒ changes sign, is discussed. The relevance of the magnetization curves over a wide range of magnetic fields and the role of H up for the study of fluctuating diamagnetism, in particular, when the first-order fluctuation correction breaks down, is pointed out. The size and temperature dependences of H up in the critical region are obtained from the experimental data and compared to the theoretical derivations for M dia .

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“…Since γ φ 1 the effect of magnetic field on W fl is always negative. In the opposite case 1 h max { , γ φ } the MT contribution dominates 11 : intrinsic pair-breaking here is weak while the effect of magnetic field on the motion of Cooper pairs is not yet strong enough:…”

Section: Resultsmentioning

confidence: 95%

“…(2), (10), (11), and (15). Here, the upper limit of summation over bosonic frequencies contains the external frequency and one should be cautious with the analytic continuation to the upper half-plane of complex frequencies.…”

Section: Re(z)mentioning

confidence: 99%

Effect of fluctuations on the NMR relaxation beyond the Abrikosov vortex state

Glatz¹,

Galda²,

Varlamov³

2015

Phys. Rev. B

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The effect of fluctuations on the nuclear magnetic resonance (NMR) relaxation rate W = T −1 1 is studied in a complete phase diagram of a 2D superconductor above the upper critical field line Hc2(T ) . In the region of relatively high temperatures and low magnetic fields, the relaxation rate W is determined by two competing effects. The first one is its decrease in result of suppression of quasiparticle density of states (DOS) due to formation of fluctuation Cooper pairs (FCP). The second one is a specific, purely quantum, relaxation process of the Maki-Thompson (MT) type, which for low field leads to an increase of the relaxation rate. The latter describes particular fluctuation processes involving self-pairing of a single electron on self-intersecting trajectories of a size up to phase-breaking length φ which becomes possible due to an electron spin-flip scattering event at a nucleus. As a result, different scenarios with either growth or decrease of the NMR relaxation rate are possible upon approaching the normal metal -type-II superconductor transition. The character of fluctuations changes along the line Hc2(T ) from the thermal long-wavelength type in weak magnetic fields to the clusters of rotating FCP in fields comparable to Hc2(0). We find that below the well-defined temperature T * 0 ≈ 0.6Tc0, the MT process becomes ineffective even in absence of intrinsic pair-breaking. The small scale of FCP rotations (ξxy) in so high fields impedes formation of long ( φ ) self-intersecting trajectories, causing the corresponding relaxation mechanism to lose its efficiency. This reduces the effect of superconducting fluctuations in the domain of high fields and low temperatures to just the suppression of quasi-particle DOS, analogously to the Abrikosov vortex phase below the Hc2(T ) line.

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Magnetic field dependence of the superconducting fluctuation contribution to NMR-NQR relaxation

Cited by 31 publications

References 27 publications

Fluctuation spectroscopy: From Rayleigh-Jeans waves to Abrikosov vortex clusters

Fluctuation spectroscopy: From Rayleigh-Jeans waves to Abrikosov vortex clusters

Zero-dimensional superconducting fluctuations and fluctuating diamagnetism in lead nanoparticles

Effect of fluctuations on the NMR relaxation beyond the Abrikosov vortex state

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