Nonlocal Meissner screening

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

doi:10.1016/j.physb.2005.11.065

Cited by 5 publications

(5 citation statements)

References 11 publications

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“…In the Meissner phase, the flux penetration is non-exponential (even exhibiting a reversal of field in a subsurface layer, according to modifications to the BCS theory due to A B Pippard). The penetration profile is mapped explicitly using low energy muons, by varying their implantation energy (Suter et al 2006). (Other prospects for this important technical development are reviewed, for instance, by Morenzoni et al 2003).…”

Section: Tin and Lead 60mentioning

confidence: 99%

Muonium as a model for interstitial hydrogen in the semiconducting and semimetallic elements

2009

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Although the interstitial hydrogen atom would seem to be one of the simplest defect centres in any lattice, its solid state chemistry is in fact unknown in many materials, not least amongst the elements. In semiconductors, the realization that hydrogen can profoundly influence electronic properties even as a trace impurity has prompted its study by all available means-but still only in the functionally important or potentially important materials-for the elements, Si, Ge and diamond. Even here, it was not studies of hydrogen itself but of its pseudo-isotope, muonium, that first provided the much needed microscopic pictures of crystallographic site and local electronic structure-now comprehensively confirmed by ab initio computation and such data as exists for monatomic, interstitial hydrogen centres in Si. Muonium can be formed in a variety of neutral paramagnetic states when positive muons are implanted into non-metals. The simple trapped atom is commonly only metastable. It coexists with or reacts to give defect centres with the unpaired electron in somewhat more extended orbitals. Indications of complete delocalization into effective mass states are discussed for B, α-Sn, Bi and even Ge, but otherwise all the muonium centres seen in the elemental semiconductors are deep and relatively compact. These are revealed, distinguished and characterized by µSR spectroscopy-muon spin rotation and resonance informing on sites and spin-density distributions, muon spin relaxation on motional dynamics and charge-state transitions.This Report documents the progress of µSR studies for all the semiconductors and semimetals of the p-block elements, Groups III-VI of the Periodic Table . The striking spectra and originally unanticipated results for Group IV are for the most part well known but deserve summarizing and updating; the sheer diversity of muonium states found is still remarkable, especially in carbon allotropes. The interplay of crystallographic site and charge state in Si and Ge at high temperatures, or under illumination, reflects the capture and loss of charge carriers that should model the electrical activity of monatomic hydrogen but still challenges theoretical descriptions. Spin-flip scattering of conduction electrons by the paramagnetic centres is revealed in heavily doped n-type material, as well as some modification of the local electronic structures. The corresponding spectroscopy for the solid elements of Groups III, V and VI is rather less well known and is reviewed here for the first time; a good deal of previously unpublished data is also included. Theoretical expectations and computational modelling are sparse, here. Recent results for B suggest a relatively shallow centre with molecular character; P and As show deeper quasi-atomic states, but still with substantial overlap of spin density onto surrounding host atoms. Particular attention is paid to the chalcogens. Muonium centres in Te show charge-state transitions already around room temperature; the identification of those in S and Se has been compli...

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Section: Tin and Lead 60mentioning

confidence: 99%

Muonium as a model for interstitial hydrogen in the semiconducting and semimetallic elements

2009

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“…These two materials were chosen since YBCO is a clear cut type-II superconductor (λ L ξ ) which should show an exponential decaying magnetic penetration profile 6 , whereas Pb in the clean limit should show a clear non-exponential B(z) according to equation (10). For detailed discussion and other materials investigated by the same technique, we refer the reader to [13,38,39]. The characterization of the YBCO sample was presented in section 3.…”

Section: Magnetic Field Penetration At the Surface Of Superconductorsmentioning

confidence: 99%

Nano-scale thin film investigations with slow polarized muons

Morenzoni

Prokscha

Suter

et al. 2004

J. Phys.: Condens. Matter

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Muons with 100% spin polarization and whose energy can be continuously varied from 0.5 to 30 keV provide a novel extension of the µSR technique allowing depth dependent studies of thin films and multilayered structures in the range from ∼1 to ∼200 nm. For example it is possible to study magnetic field profiles near the surface of superconductors and directly determine fundamental quantities such as the magnetic penetration depth. Low energy muons (LE-µ + ) also allow mapping the spin polarization in multilayered structures, for instance that of the conduction electrons of a non-magnetic buried layer in between thin ferromagnetic layers.

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“…After all, the Gaussian spectra of the microscopic fields implies that the Gaussian approximation, which was used to fit the spectra, is completely adequate and therefore the high-keV muons deliver correct information not only on B (as they always do [30]) but also on the muon depolarization rate σ, the damping coefficient of the µSR signal. The latter characterizes the inhomogeneity of the microscopic field over the muon sites (see [12] for details).…”

Section: Methodsmentioning

confidence: 99%

“…(4) for which Pippard suggested a non-local extension of the London theory [29]. It is also consisted with experiment [30][31][32].…”

Section: London Theorymentioning

confidence: 99%

Meissner Effect: History of Development and Novel Aspects

Кожевников

2021

Preprint

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The discovery of the Meissner (Meissner–Ochsenfeld) effect in 1933 was an incontestable turning point in the history of superconductivity. First, it demonstrated that superconductivity is an unknown before equilibrium state of matter, thus allowing to use the power of thermodynamics for its study. This provided a justification for the two-fluid model of Gorter and Casimir, a seminal thermodynamic theory founded on a postulate of zero entropy of the superconducting (S) component of conduction electrons. Second, the Meissner effect demonstrated that, apart from zero electric resistivity, the S phase is also characterized by zero magnetic induction. The latter property is used as a basic postulate in the theory of F. and H. London, which underlies the understanding of electromagnetic properties of superconductors. Here the experimental and theoretical aspects of the Meissner effect are reviewed. The reader will see that, in spite of almost nine decades age, the London theory still contains questions, the answers to which can lead to a revision of the standard picture of the Meissner state (MS) and, if so, of other equilibrium superconducting states. An attempt is made to take a fresh look at electrodynamics of the MS and try to work out with the issues associated with this the most important state of all superconductors. It is shown that the concept of Cooper's pairing along with the Bohr–Sommerfeld quantization condition allows one to construct a semi-classical theoretical model consistently addressing properties of the MS and beyond, including non-equilibrium properties of superconductors caused by the total current. As follows from the model, the three “big zeros” of superconductivity (zero resistance, zero induction and zero entropy) have equal weight and grow from a single root: quantization of the angular momentum of paired electrons. The model predicts some yet unknown effects. If confirmed, they can help in studies of microscopic properties of all superconductors. Preliminary experimental results suggesting the need to revise the standard picture of the MS are presented.

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Nonlocal Meissner screening

Cited by 5 publications

References 11 publications

Muonium as a model for interstitial hydrogen in the semiconducting and semimetallic elements

Muonium as a model for interstitial hydrogen in the semiconducting and semimetallic elements

Nano-scale thin film investigations with slow polarized muons

Meissner Effect: History of Development and Novel Aspects

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