Spin-dependent group delay time and Hartman effect in ferromagnetic bilayer graphene superlattice

We theoretically study the spin-dependent group delay time through ferromagnetic bilayer graphene superlattice in the absence and presence of the bandgap. It is found that the group delay time depends on the spin degree of freedom and exhibits an oscillatory behavior with respect to the Fermi energy and barrier width. Furthermore, in the absence of the bandgap, the superluminal or Hartman effect exists only for the normal angle of incidence. Moreover, when bandgap value is large enough [Formula: see text], the Hartman effect can be observed for all angles of incidence. These results are contrary to the observed behavior for monolayer graphene superlattice.

Superluminal Neutrinos: Experimental Data and New Interpretative Theories

In this study the data of the OPERA and MINOS experiments, together with those related to the SN1987A supernova, are discussed in the context of the recent theories proposed for the superluminal muon neutrino. It is proved that for the models in which the Lorentz symmetry is violated, the decay mechanism leading to neutrino oscillation becomes possible. Within this framework, a new model based on the Hartman effect is proposed, according to which the neutrino becomes superluminal by quantum tunnelling, crossing a potential barrier generated by its interaction with the earth's crust matter. This model does not violate the Lorentz symmetry since the tachyonic state is generated by the quantum fluctuation of the neutrino initial energy, even if it requires to conjecture the presence of a quantum field that we ascribe to be that due to dark matter. In this model all superluminal neutrino decay mechanisms proposed in other studies are allowed. The hypothetical boson mediating the interaction between neutrino and dark matter is also discussed.

Analysis of wavepacket tunneling with the method of Laplace transformation

We use the method of Laplace transformation to determine the dynamics of a wavepacket that passes a barrier by tunneling. We investigate the transmitted wavepacket and find that it can be resolved into a sequence of subsequent wave packages. This result sheds new light on the Hartman effect for the tunneling time and gives a possible explanation for an experimental result obtained by Spielmann et al.