937 research outputs found
Long-range supercurrents through a chiral non-collinear antiferromagnet in lateral Josephson junctions
The proximity-coupling of a chiral non-collinear antiferromagnet (AFM)1,2,3,4,5 with a singlet superconductor allows spin-unpolarized singlet Cooper pairs to be converted into spin-polarized triplet pairs6,7,8, thereby enabling non-dissipative, long-range spin correlations9,10,11,12,13,14. The mechanism of this conversion derives from fictitious magnetic fields that are created by a non-zero Berry phase15 in AFMs with non-collinear atomic-scale spin arrangements1,2,3,4,5. Here we report long-ranged lateral Josephson supercurrents through an epitaxial thin film of the triangular chiral AFM Mn3Ge (refs. 3,4,5). The Josephson supercurrents in this chiral AFM decay by approximately one to two orders of magnitude slower than would be expected for singlet pair correlations9,10,11,12,13,14 and their response to an external magnetic field reflects a clear spatial quantum interference. Given the long-range supercurrents present in both single- and mixed-phase Mn3Ge, but absent in a collinear AFM IrMn16, our results pave a way for the topological generation of spin-polarized triplet pairs6,7,8 via Berry phase engineering15 of the chiral AFMs
Layered ferromagnet-superconductor structures: the state and proximity effects
We investigate clean mutilayered structures of the SFS and SFSFS type, (where
the S layer is intrinsically superconducting and the F layer is ferromagnetic)
through numerical solution of the self-consistent Bogoliubov-de Gennes
equations for these systems. We obtain results for the pair amplitude, the
local density of states, and the local magnetic moment. We find that as a
function of the thickness of the magnetic layers separating adjacent
superconductors, the ground state energy varies periodically between two stable
states. The first state is an ordinary "0-state", in which the order parameter
has a phase difference of zero between consecutive S layers, and the second is
a "-state", where the sign alternates, corresponding to a phase difference
of between adjacent S layers. This behavior can be understood from simple
arguments. The density of states and the local magnetic moment reflect also
this periodicity.Comment: 12 pages, 10 Figure
Spontaneous Spin Polarized Currents in Superconductor-Ferromagnetic Metal Heterostructures
We study a simple microscopic model for thin, ferromagnetic, metallic layers
on semi-infinite bulk superconductor. We find that for certain values of the
exchange spliting, on the ferromagnetic side, the ground states of such
structures feature spontaneously induced spin polarized currents. Using a
mean-field theory, which is selfconsistent with respect to the pairing
amplitude , spin polarization and the spontaneous current
, we show that not only there are Andreev bound states in the
ferromagnet but when their energies are near zero they support
spontaneous currents parallel to the ferromagnetic-superconducting interface.
Moreover, we demonstrate that the spin-polarization of these currents depends
sensitively on the band filling.Comment: 4 pages, 5 Postscript figures (included
Measurement of the 58Ni(α, γ) 62Zn reaction and its astrophysical impact
Funding Details: PHY 08-22648, NSF, National Science Foundation; PHY 0969058, NSF, National Science Foundation; PHY 1102511, NSF, National Science FoundationCross section measurements of the 58Ni(α,γ)62Zn reaction were performed in the energy range Eα=5.5to9.5 MeV at the Nuclear Science Laboratory of the University of Notre Dame, using the NSCL Summing NaI(Tl) detector and the γ-summing technique. The measurements are compared to predictions in the statistical Hauser-Feshbach model of nuclear reactions using the SMARAGD code. It is found that the energy dependence of the cross section is reproduced well but the absolute value is overestimated by the prediction. This can be remedied by rescaling the α width by a factor of 0.45. Stellar reactivities were calculated with the rescaled α width and their impact on nucleosynthesis in type Ia supernovae has been studied. It is found that the resulting abundances change by up to 5% when using the new reactivities. © 2014 American Physical Society.Peer reviewe
'Diverse mobilities': second-generation Greek-Germans engage with the homeland as children and as adults
This paper is about the children of Greek labour migrants in Germany. We focus on two life-stages of âreturnâ for this second generation: as young children brought to Greece on holidays or sent back for longer periods, and as young adults exercising an independent âreturnâ migration. We draw both on literature and on our own field interviews with 50 first- and second-generation Greek-Germans. We find the practise of sending young children back to Greece to have been surprisingly widespread yet little documented. Adult relocation to the parental homeland takes place for five reasons: (i) a âsearch for selfâ; (ii) attraction of the Greek way of life; (iii) the actualisation of the âfamily narrative of returnâ by the second, rather than the first, generation; (iv) life-stage events such as going to university or marrying a Greek; (v) escape from a traumatic event or oppressive family situation. Yet the return often brings difficulties, disillusionment, identity reappraisal, and a re-evaluation of the German context
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