1,721,113 research outputs found
Hopping-resolved electron-phonon coupling in bilayer graphene
No full textIn this paper we investigate the electron-phonon coupling in bilayer graphene, as a paradigmatic case for multilayer graphenes where interlayer hoppings are relevant. Using a frozen-phonon approach within the context of density functional theory (DFT) and using different optical phonon displacements, we are able to evaluate quantitatively the electron-phonon coupling alpha(i) associated with each hopping term gamma(i). This analysis also reveals a simple scaling law between the hopping terms gamma(i) and the electron-phonon coupling alpha(i) which goes beyond the specific DFT technique employed
Symmetry breaking in vanadium trihalides
Full text linkIn the light of new experimental evidence we study the insulating ground state of the 3d2 -transition metal trihalides VX 3 (X = Cl, I). Based on density functional theory with the Hubbard correction we systematically show how these systems host multiple metastable states characterised by different orbital ordering and electronic behaviour. Our calculations reveal the importance of imposing a precondition in the on site d density matrix and of considering a symmetry broken unit cell to correctly take into account the correlation effects in a mean field framework. Furthermore we ultimately found a ground state with the a1g orbital occupied in a distorted VX 6 octahedra driven by an optical phonon mode
Effects of nonhydrostatic pressure on the structural and magnetic properties of BaFe(2)As(2)
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Magnetic properties of Fe-pnictides superconductors as a function of pressure and doping
No full textWe present a first principles study of the electronic and magnetic properties of Fe-based pnicitdes superconductors as a function of pressure and doping. We show that the magnetic phase and a local magnetic moment persists at doping level quite larger than what found in experiments and the pressure phase diagram consists of a paramagnetic, antiferromagnetic and non-magnetic phases.
Although this result calls for the inclusion of long-wavelength or local fluctuations of iron magnetic moment and non-hydrostatic pressure effects, in order to improve the theoretical description of real experimental conditions, recent photoemission experiments[1] reconcile these DFT results, showing a local magnetic moment on Fe site different from zero in the paramagnetic, antiferromagnetic and the superconducting phase
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