A.S. Vasenko
S. Kawabata
A. Ozaeta
A.A. Golubov
V.S. Stolyarov
F.S. Bergeret
F.W.J. Hekking
Abstract Ferromagnetic materials with exchange fields E ex smaller or of the order of the superconducting gap Δ are important for applications of corresponding (s-wave) superconductor/ferromagnet/superconductor (SFS) junctions. Presently such materials are not known but there are several proposals how to create them. Small exchange fields are in principle difficult to detect. Based on our results we propose reliable detection methods of such small E ex . For exchange fields smaller than the superconducting gap the subgap differential conductance of the normal metal–ferromagnet–insulator–superconductor (NFIS) junction shows a peak at the voltage bias equal to the exchange field of the ferromagnetic layer, eV = E ex . Thus measuring the subgap conductance one can reliably determine small E ex < Δ . In the opposite case E ex > Δ one can determine the exchange field in scanning tunneling microscopy (STM) experiment. The density of states of the FS bilayer measured at the outer border of the ferromagnet shows a peak at the energy equal to the exchange field, E = E ex . This peak can be only visible for small enough exchange fields of the order of few Δ . Highlights • We summarize different proposals to create ferromagnets with small exchange fields. • We propose methods to measure small exchange fields in F/S structures. • Exchange fields smaller than the gap can be detected by measuring the dI/dV. • Exchange fields larger than the gap can be detected in STM experiments.
In this letter I present my point of view about the importance of contextualization of physics and its outspread over society in the teaching of physics. I point my questioning about the real origin of disciplinas like =E2=80=9Cscience, technologie and society=E2=80=9D (CTS) and =E2=80=9Cscientific and technological alphabetization=E2=80=9D (ACT), arguing that maybe one should discuss the structure of teaching physics instead of =E2=80=9Cadd=E2=80=9D one step that aims to correct the lack we have created between physics and society. Many theoretical have remembered that CTS and ACT were born from a Freirean point of view about teaching, however what we have seen in practical is the insistence in the method and bibliographies older than this pedagogical movement.=09
Kundu, Sumana
Yadav, Ram Manohar
Narayanan, T. N.
Shelke, Manjusha V.
Vajtai, Robert
Ajayan, P. M.
Pillai, Vijayamohanan K.
Graphene quantum dots (GQDs) are a promising category of materials with remarkable size dependent properties like tunable bandgap and photoluminescence along with the possibility of effective chemical functionalization. Doping of GQDs with heteroatoms is an interesting way of regulating their properties. Herein, we report a facile and scalable one-step synthesis of luminescent GQDs, substitutionally co-doped with N, F and S, of similar to 2 nm average size by a microwave treatment of multi-walled carbon nanotubes in a customized ionic liquid medium. The use of an ionic liquid coupled with the use of a microwave technique enables not only an ultrafast process for the synthesis of co-doped GQDs, but also provides excellent photoluminescence quantum yield (70%), perhaps due to the interaction of defect clusters and dopants.
We study the hadronic (B) over bar (0)(s) decays based on the existence of the resonant state f(J) (2220). In particular, we are able to explain the unexpected large experimental result of (B) over bar (0)(s) -> J/psi p (p) over bar) =3D (3.0(-1.1)(+1.2) +/- 0.52 +/- 0.03) x 10(-6) measured recently by the LHCb collaboration due to the resonant contribution in (B) over bar (0)(s) -> J/psi f(J) (2220) with f(J) (2220) -> p (p) over bar, while it is estimated to be at most of order 10(-9) in terms of the OZI rule without the resonance. In addition, we find that B((B) over bar (0)(s) -> D*(0)(f(J) ->) p (p) over bar) =3D (4.70 +/- 2.89) x 10(-7), B((B) over bar (0)(s) -> J/psi(f(J) ->) pi pi) =3D (15.6 +/- 15.2) x 10(-6), and B((B) over bar (0)(s) -> D*(0)(f(J) ->) pi pi) =3D (24.5 +/- 24.4) x 10(-7), while B((B) over bar (0)(s) -> J/psi(f(J) ->) K (K) over bar) < 1.6 x 10(-5) and B(<(B)over bar>(0)(s) -> D*(0)(f(J) ->) K (K) over bar) < 2.5x10(-6). Moreover, wepredict that the decay branching ratios of <(B)over bar>(0)(s) -> (J/psi, D*(0)) Lambda(Lambda) over bar are (2.68 +/- 1.23) x 10(-7) and (2.25 +/- 0.80) x 10(-6). Some of the predicted (B) over bar (0)(s) decays are accessible to the experiments at the LHCb.
We construct new examples of expander Cayley graphs of finite groups, arising as congruence quotients of non-elementary subgroups of modulo certain square-free ideals. We describe some applications of our results to simple random walks on such subgroups, specifically giving bounds on the rate of escape of such walks from algebraic subvarieties, the set of squares and the set of elements with reducible characteristic polynomial in .