17 research outputs found
Josephson coupling through ferromagnetic heterojunctions with noncollinear magnetizations
We study the Josephson effect in clean heterojunctions that consist of
superconductors connected through two metallic ferromagnets with insulating
interfaces. We solve the scattering problem based on the Bogoliubov--de Gennes
equation for any relative orientation of in-plane magnetizations, arbitrary
transparency of interfaces, and mismatch of Fermi wave vectors. Both spin
singlet and triplet superconducting correlations are taken into account, and
the Josephson current is calculated as a function of the ferromagnetic layers
thicknesses and of the angle between their magnetizations. We find
that the critical Josephson current is a monotonic function of
when the junction is far enough from transitions. This holds when
ferromagnets are relatively weak. For stronger ferromagnets, variation of
induces switching between 0 and states and is
non-monotonic function, displaying characteristic dips at the transitions.
However, the non-monotonicity is the effect of a weaker influence of the
exchange potential in the case of non-parallel magnetizations. No substantial
impact of spin-triplet superconducting correlations on the Josephson current
has been found in the clean limit. Experimental control of the critical current
and transitions by varying the angle between magnetizations is
suggested.Comment: 7 pages, 8 figure
Superconducting spintronics
The interaction between superconducting and spin-polarized orders has recently emerged as a major research field following a series
of fundamental breakthroughs in charge transport in superconductor-ferromagnet heterodevices which promise new device
functionality. Traditional studies which combine spintronics and superconductivity have mainly focused on the injection of
spin-polarized quasiparticles into superconducting materials. However, a complete synergy between superconducting and magnetic
orders turns out to be possible through the creation of spin-triplet Cooper pairs which are generated at carefully engineered
superconductor interfaces with ferromagnetic materials. Currently, there is intense activity focused on identifying materials
combinations which merge superconductivity and spintronics in order to enhance device functionality and performance. The results
look promising: it has been shown, for example, that superconducting order can greatly enhance central effects in spintronics such as
spin injection and magnetoresistance. Here, we review the experimental and theoretical advances in this field and provide an outlook
for upcoming challenges related to the new concept of superconducting spintronics.J.L. was supported by the Research Council of Norway, Grants No. 205591 and 216700.
J.W.A.R. was supported by the UK Royal Society and the Leverhulme Trust through an
International Network Grant (IN-2013-033).This is the accepted manuscript. The final version is available at http://www.nature.com/nphys/journal/v11/n4/full/nphys3242.html
"Adaptive response" - some underlying mechanisms and open questions
Organisms are affected by different DNA damaging agents naturally present in the environment or released as a result of human activity. Many defense mechanisms have evolved in organisms to minimize genotoxic damage. One of them is induced radioresistance or adaptive response. The adaptive response could be considered as a nonspecific phenomenon in which exposure to minimal stress could result in increased resistance to higher levels of the same or to other types of stress some hours later. A better understanding of the molecular mechanism underlying the adaptive response may lead to an improvement of cancer treatment, risk assessment and risk management strategies, radiation protection, e. g. of astronauts during long-term space flights. In this mini-review we discuss some open questions and the probable underlying mechanisms involved in adaptive response: the transcription of many genes and the activation of numerous signaling pathways that trigger cell defenses - DNA repair systems, induction of proteins synthesis, enhanced detoxification of free radicals and antioxidant production.Publisher PDFPeer reviewe