SKM 2023 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 21: Correlated Electrons: Electronic Structure Calculations
TT 21.4: Vortrag
Dienstag, 28. März 2023, 10:15–10:30, HSZ 201
New superexchange paths due to synergetic breathing and hopping in corner-sharing cuprates — •Nikolay A. Bogdanov1, Giovanni Li Manni1, Sandeep Sharma1,2, Olle Gunnarsson1, and Ali Alavi1,3 — 1Max Planck Institute for Solid State Research, Stuttgart, Germany — 2Department of Chemistry, University of Colorado Boulder, Boulder, CO, USA — 3University Chemical Laboratory, Cambridge, UK
We present ab initio quantum chemistry calculations of the nearest-neighbour superexchange antiferromagnetic spin coupling J for two cuprates, Sr2CuO3 and La2CuO4. Good agreement with experimental estimates is obtained for both systems. We also find that J increases substantially as the distance between Cu and apical O is increased.
Analysis of the correlated wavefunctions together with extended superexchange models shows that there is an important synergetic effect of the Coulomb interaction and the O–Cu hopping. When an extra electron hops into Cu 3d orbital, Coulomb interaction leads to the orbital breathing (expansion), which on its turn reinforces electron hopping. This correlated breathing-enhanced hopping mechanism is a new ingredient in superexchange models. Our analysis shows that suppression of the described mechanism leads to a drastic reduction in the antiferromagnetic coupling, indicating that it is of primary importance in generating the strong interactions.