648 research outputs found
Identifying topological-band insulator transitions in silicene and other 2D gapped Dirac materials by means of R\'enyi-Wehrl entropy
We propose a new method to identify transitions from a topological insulator
to a band insulator in silicene (the silicon equivalent of graphene) in the
presence of perpendicular magnetic and electric fields, by using the
R\'enyi-Wehrl entropy of the quantum state in phase space. Electron-hole
entropies display an inversion/crossing behavior at the charge neutrality point
for any Landau level, and the combined entropy of particles plus holes turns
out to be maximum at this critical point. The result is interpreted in terms of
delocalization of the quantum state in phase space. The entropic description
presented in this work will be valid in general 2D gapped Dirac materials, with
a strong intrinsic spin-orbit interaction, isoestructural with silicene.Comment: to appear in EP
Searching for pairing energies in phase space
We obtain a representation of pairing energies in phase space, for the
Lipkin-Meshkov-Glick and general boson Bardeen-Cooper-Schrieffer pairing
models. This is done by means of a probability distribution of the quantum
state in phase space. In fact, we prove a correspondence between the points at
which this probability distribution vanishes and the pairing energies. In
principle, the vanishing of this probability distribution is experimentally
accessible and additionally gives a method to visualize pairing energies across
the model control parameter space. This result opens new ways to experimentally
approach quantum pairing systems.Comment: 5 pages, 4 figure
Wave packet revivals in a graphene quantum dot in a perpendicular magnetic field
We study the time-evolution of localized wavepackets in graphene quantum dots
under a perpendicular magnetic field, focusing on the quasiclassical and
revival periodicities, for different values of the magnetic field intensities
in a theoretical framework. We have considered contributions of the two
inequivalent points in the Brillouin zone. The revival time has been found as
an observable that shows the break valley degeneracy.Comment: 5 pages, 4 figures, corrected typo, To appear in Phys. Rev.
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