1,070 research outputs found
Electron-phonon vertex and its influence on the superconductivity of two-dimensional metals on a piezoelectric substrate
We investigate the interaction between the electrons of a two-dimensional
metal and the acoustic phonons of an underlying piezoelectric substrate.
Fundamental inequalities can be obtained from general energy arguments. As a
result, phonon mediated attraction can be proven to never overcome electron
Coulomb repulsion, at least for long phonon wavelengths. We study the influence
of these phonons on the possible pairing instabilities of a two-dimensional
electron gas such as graphene.Comment: 10 pages, 3 figure
Intrinsic frustration effects in anisotropic superconductors
Lattice distortions in which the axes are locally rotated provide an
intrinsic source of frustration in anisotropic superconductors. A general
framework to study this effect is presented. The influence of lattice defects
and phonons in and layered superconductors is studied.Comment: enlarged versio
Topological superconductivity in lead nanowires
Superconductors with an odd number of bands crossing the Fermi energy have
topologically protected Andreev states at interfaces, including Majorana states
in one dimensional geometries. Superconductivity, a low number of 1D channels,
large spin orbit coupling, and a sizeable Zeeman energy, are present in lead
nanowires produced by nanoindentation of a Pb tip on a Pb substrate, in
magnetic fields higher than the Pb bulk critical field. A number of such
devices have been analyzed. In some of them, the dependence of the critical
current on magnetic field, and the Multiple Andreev Reflections observed at
finite voltages, are compatible with the existence of topological
superconductivity
Many-body effects in doped graphene on a piezoelectric substrate
We investigate the many-body properties of graphene on top of a piezoelectric
substrate, focusing on the interaction between the graphene electrons and the
piezoelectric acoustic phonons. We calculate the electron and phonon
self-energies as well as the electron mobility limited by the substrate
phonons. We emphasize the importance of the proper screening of the
electron-phonon vertex and discuss the various limiting behaviors as a function
of electron energy, temperature, and doping level. The effect on the graphene
electrons of the piezoelectric acoustic phonons is compared with that of the
intrinsic deformation acoustic phonons of graphene. Substrate phonons tend to
dominate over intrinsic ones for low doping levels at high and low
temperatures.Comment: 13 pages, 8 figure
Orthogonality catastrophe and Kondo effect in graphene
Anderson's orthogonality catastrophe in graphene, at energies close to the
Dirac point, is analyzed. It is shown that, in clean systems, the orthogonality
catastrophe is suppressed, due to the vanishing density of states at the Dirac
point. In the presence of preexisting localized states at the Dirac energy, the
orthogonality catastrophe shows similar features to those found in normal
metals with a finite density of states at the Fermi level. The implications for
the Kondo effect induced by magnetic impurities, and for the Fermi edge
singularities in tunneling processes are also discussed.Comment: 7 pages, 7 figure
Many body effects in finite metallic carbon nanotubes
The non homogeneity of the charge distribution in a carbon nanotube leads to
the formation of an excitonic resonance, in a similar way to the one observed
in X-ray absorption in metals. As a result, a positive anomaly at low bias
appears in the tunnelling density of states. This effect depends on the
screening of the electron--electron interactions by metallic gates, and it
modifies the coupling of the nanotube to normal and superconducting electrodes.Comment: 5 page
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