Are superconductivity mechanisms a matter for chemists?
Language
en
Article de revue
This item was published in
Condensed Matter. 2020-12, vol. 5, n° 4, p. 67 (30 p.)
MDPI
English Abstract
From a tight-binding approach to the instability of nonbonding electronic states, along a double-well potential, we consider here how the coupling of these states with a phonon mode can open a superconducting gap at the ...Read more >
From a tight-binding approach to the instability of nonbonding electronic states, along a double-well potential, we consider here how the coupling of these states with a phonon mode can open a superconducting gap at the Fermi level. The alternation of broken- and unbroken-symmetry states, along the phonon breathing distortion, induces the mixing of band-edge states on a very short timescale, according to the noncrossing rule of chemists. We show that this mixing may generate cationic and anionic disproportionation. The negative U mechanism is thus justified here, leading to the mixing of occupied and unoccupied pair states, for the opening of a 2Δ superconducting gap. The closeness of broad σ * and narrow π * bands in the vicinity of the Fermi level should favor the superconducting phase over the insulating or metallic state, in agreement with Micnas et al.’s studies. We applied this approach to several families of superconducting materials, i.e., doped strontium titanate, high-TC cuprates and iron selenide.Read less <
English Keywords
nonbonding electrons
noncrossing rule
negative-u mechanism
phonons
BCS theory
disproportionation
hole pairing
cuprates
titanates
iron selenide
Origin
Hal imported