Direct Observation of Nonlocal Effects in a Superconductor

Suter, A.; Morenzoni, E.; Khasanov, R.; Luetkens, H.; Prokscha, T.; Garifianov, N.

doi:10.1103/physrevlett.92.087001

Cited by 41 publications

(69 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The nonlocal effect has been unambiguously confirmed for the first time by LE-µSR measurements on Pb, Ta and Nb 3,18 , and soon after by PNR measurements in In 10 . In Refs.…”

Section: Introductionmentioning

confidence: 57%

Nonlocal effect and dimensions of Cooper pairs measured by low-energy muons and polarized neutrons in type-I superconductors

et al. 2013

Self Cite

View full text Add to dashboard Cite

The Pippard coherence length ξ0 (the size of a Cooper pair) in two extreme type-I superconductors (In and Sn) was determined directly through high-resolution measurement of the nonlocal electrodynamic effect combining low-energy muon spin rotation spectroscopy and polarized neutron reflectometry. The renormalization factor Z ≡ m * cp /2m (m * cp and m are the mass of the Cooper pair and the electron, respectively) resulting from the electron-phonon interaction, and the temperature dependent London penetration depth λL(T ) were determined as well. An expression linking ξ0, Z and λL(0) is introduced and experimentally verified. This expression allows one to determine experimentally the Pippard coherence length in any superconductor, independent of whether the superconductor is local or nonlocal, conventional or unconventional.

show abstract

“…The nonlocal effect has been unambiguously confirmed for the first time by LE-µSR measurements on Pb, Ta and Nb 3,18 , and soon after by PNR measurements in In 10 . In Refs.…”

Section: Introductionmentioning

confidence: 57%

Nonlocal effect and dimensions of Cooper pairs measured by low-energy muons and polarized neutrons in type-I superconductors

et al. 2013

Self Cite

View full text Add to dashboard Cite

show abstract

“…For this, we used the technique of low-energy muon spin rotation 16,17 (LE-μSR), which has previously been applied successfully to obtain the depth-resolved profile of the local magnetization in various thin films and heterostructures 18,19 . The stopping distribution of the fully spin-polarized muons can be varied here on the scale of about 3-200 nm through the control of the muon implantation energy.…”

Section: Measurement Of Spin Penetrationmentioning

confidence: 99%

Direct measurement of the electronic spin diffusion length in a fully functional organic spin valve by low-energy muon spin rotation

et al. 2008

Self Cite

View full text Add to dashboard Cite

Electronic devices that use the spin degree of freedom hold unique prospects for future technology. The performance of these 'spintronic' devices relies heavily on the efficient transfer of spin polarization across different layers and interfaces. This complex transfer process depends on individual material properties and also, most importantly, on the structural and electronic properties of the interfaces between the different materials and defects that are common to real devices. Knowledge of these factors is especially important for the relatively new field of organic spintronics, where there is a severe lack of suitable experimental techniques that can yield depth-resolved information about the spin polarization of charge carriers within buried layers of real devices. Here, we present a new depth-resolved technique for measuring the spin polarization of current-injected electrons in an organic spin valve and find the temperature dependence of the measured spin diffusion length is correlated with the device magnetoresistance.R ecently great efforts have been undertaken to use the spin degree of freedom in electronic devices. These activities are fuelled by the potential prospects of spin-electronic (or 'spintronic') devices for example in terms of increased processing speed and integration, non-volatility, reduced power consumption, multifunctionality and their suitability for quantum computing 1 . The most common method for using the spin in devices is based on the alignment of the electron spin ('up' or 'down') relative to either a reference magnetic field or the magnetization orientation of a ferromagnetic layer. Device operation normally proceeds with measuring a quantity such as the electrical current that depends on how the degree of spin alignment is transferred across the device. The so-called 'spin valve' is a prominent example of such a spin-enabled device that has already revolutionized hard-drive read heads and magnetic memory 1 . The efficient transfer of spin polarization in real device structures remains one of the most difficult challenges in spintronics, because it is dependent on more than just the properties of the individual materials that comprise the device.Recently 2,3 , the use of organic materials in spintronics has become of significant interest, primarily owing to their ease and small cost of processing and electronic and structural flexibility. Furthermore, the extremely long spin coherence times found in organic materials offer considerable advantages over other materials 3 . This favourable property is related to two factors, first the weak spin-orbit coupling of light elements such as carbon and second to the small nuclear hyperfine interaction 4,5 . The latter arises because the electron transport in π-conjugated molecules is normally confined to molecular states, delocalized to the carbon rings, the predominant isotope of which, 12 C, has zero nuclear spin 4 .A common way to measure spin diffusion is based on time-resolved optical techniques, where spin-polarized charge carrie...

show abstract

“…All these findings were confirmed by the microscopic BCS theory 4 . Although these theoretical predictions have been known for half a century, only very recently has a "direct" measurement of the functional dependence of B(z) been demonstrated 5 . A historical summary of the experimental work on this subject begins with that of Sommerhalder and co-worker 6,7,8 who showed the existence of a sign reversal of B(z) by measuring the magnetic field leaking through a very thin superconducting tin film.…”

Section: Introductionmentioning

confidence: 99%

Observation of nonexponential magnetic penetration profiles in the Meissner state: A manifestation of nonlocal effects in superconductors

et al. 2005

Self Cite

View full text Add to dashboard Cite

Implanting fully polarized low energy muons on the nanometer scale beneath the surface of a superconductor in the Meissner state enabled us to probe the evanescent magnetic field profile B(z) (0 < z 200nm measured from the surface). All the investigated samples [Nb: κ ≃ 0.7(2), Pb:κ ≃ 0.6(1), Ta: κ ≃ 0.5(2)] show clear deviations from the simple exponential B(z) expected in the London limit, thus revealing the non-local response of these superconductors. From a quantitative analysis within the Pippard and BCS models the London penetration depth λL is extracted. In the case of Pb also the clean limit coherence length ξ0 is obtained. Furthermore we find that the temperature dependence of the magnetic penetration depth follows closely the two-fluid expectation 1/λ 2 ∝ 1 − (T /Tc) 4 . While B(z) for Nb and Pb are rather well described within the Pippard and BCS models, for Ta this is only true to a lesser degree. We attribute this discrepancy to the fact that the superfluid density is decreased by approaching the surface on a length scale ξ0. This effect, which is not taken self-consistently into account in the mentioned models, should be more pronounced in the lowest κ regime consistently with our findings.

show abstract

Direct Observation of Nonlocal Effects in a Superconductor

Cited by 41 publications

References 24 publications

Nonlocal effect and dimensions of Cooper pairs measured by low-energy muons and polarized neutrons in type-I superconductors

Nonlocal effect and dimensions of Cooper pairs measured by low-energy muons and polarized neutrons in type-I superconductors

Direct measurement of the electronic spin diffusion length in a fully functional organic spin valve by low-energy muon spin rotation

Observation of nonexponential magnetic penetration profiles in the Meissner state: A manifestation of nonlocal effects in superconductors

Contact Info

Product

Resources

About