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Free keywords:
superconductivity; flat/steep band; mercury; magnesium diboride
Abstract:
Based on chemical bonding considerations in a crystalline solid, a
Hamiltonian was proposed for the "flat/steep band" scenario. This model
has been studied with the first-principles method. With Hg and MgB2 as
examples, we have explained the characteristics of this model and
observed peak-like structure of the electron-phonon coupling constant
lambda(q) in q space. The strong coupling of the "flat band" electrons
with phonons has been corroborated by developing a new functional
Psib(Phi), through which we can quantitatively compare different
electronic states in coupling to a specific phonon. In the case of MgB2
a multigap structure of the superconducting state results from our
model.
