Wess–Zumino supersymmetric phase and superconductivity in graphene

Supersymmetry is expected to exist in nature at high energies, but must be spontaneously broken at ordinary energy scales. The required energy scale in elementary particle physics is currently inaccessible, but condensed matter could furnish low energy realizations of supersymmetry. In graphene, electrons behave as ‘relativistic’ massless fermions in 1+2$1+2$ dimensions. Here we propose phenomenologically, assuming that some microscopic parameters can be fine-tuned in graphene, the existence of a supersymmetric Wess–Zumino phase. The supersymmetry breaking leads to a superconductor phase, described by a relativistic Ginzburg–Landau phenomenology.     

The Dirac Equation in Six-dimensional <Emphasis Type="Italic">SO</Emphasis>(3,3) Symmetry Group and a Non-chiral “Electroweak” Theory

We propose a model of electroweak interactions without chirality in a six-dimensional spacetime with 3 time-like and 3 space-like coordinates, which allows a geometrical meaning for gauge symmetries. The spacetime interval ds ²=dx _μ dx ^μ is left invariant under the symmetry group SO(3,3). We obtain the six-dimensional version of the Dirac gamma matrices, Γ _μ , and write down a Dirac-like Lagrangian density, \(\mathcal{L}=i\bar{\psi}\Gamma ^{\mu }\nabla _{\mu }\psi\). The spinor ψ can be decomposed into two Dirac spinors, ψ ₁ and ψ ₂, interpreted as the electron and neutrino fields, respectively. In six-dimensional spacetime the electron and neutrino fields appear as parts of the same entity in a natural manner. The SO(3,3) Lorentz symmetry group is locally broken to the observable SO(1,3) Lorentz group, with only one observable time component, t _z . The t _z -axis may not be the same at all points of the spacetime, and the effect of breaking the SO(3,3) spacetime symmetry group locally to an SO(1,3) Lorentz group, is perceived by the observers as the existence of the gauge fields. We interpret the origin of mass and gauge interactions as a consequence of extra time dimensions, without the need of introducing the so-called Higgs mechanism for the generation of mass. Further, in our ‘toy’ model, we are able to give a geometric meaning to the electromagnetic and non-Abelian gauge symmetries.     

On the Coexistence of Superconductivity and Magnetic Ordering in Unconventional Superconductors

It is demonstrated that the coexistence of superconductivity and magnetic ordering, occurring, for instance, in iron-based pnictides and uranium compounds, is not forbidden by classical Maxwell’s equations and London-type equations. It predicts simply that internal magnetization is allowed but localized magnetic moments are screened at distances of the order of the London penetration depth. A microscopic theory is considered for the case of ferromagnetic ordering, described in simple terms by electron-magnon coupling. For the sake of simplicity, we assume that itinerant electrons are not responsible for the magnetic ordering, but interact with phonon and magnon excitations, leading to an alternative Cooper pair channel. The temperature dependence and the isotope effect of the superconducting gap is also analysed.     

Comprehensive analysis of maté (Ilex paraguariensis) compounds: development of chemical strategies for matesaponin analysis by mass spectrometry

Ilex paraguariensis (maté) is an important plant from southern Brazil, Paraguay, Uruguay and Argentina, where its leaves are widely used in hot or cold beverages. We now present a comprehensive ULPC-PDA-MS analysis of the compounds found in its leaves. The analysis was rapid, less than 13 min and many compounds were identified, among these, the chlorogenic acid series, and other quinic acid derivatives, xanthines, and several saponins, many of which have not been previously described, including many isomers. The isomerism could occur in the aglycone moiety, namely ursolic or oleanolic acid, or in the carbohydrate moiety. Additionally, many acetylated saponins were detected. The structure of known and novel saponins was determined using per-O-methylation with ESI-MS analysis, as well as with GC-MS of their partially O-methylated alditol acetate (PMAA) derivatives, along with ESI-MS analysis of the O-isopropylidene (IPP) derivatives provided fundamental information on interglycosidic linkages, avoiding the purification steps.