2018/03/19 by Bogdanov, Nikolay A., Manni, Giovanni Li, Sharma, Sandeep +2
#FOS: Physical sciences #Strongly Correlated Electrons (cond-mat.str-el)
paper · doi:10.48550/arxiv.1803.07026
We present ab initio calculations of the superexchange antiferromagnetic spin coupling J for two cuprates, Sr2CuO3 and La2CuO4. Good agreement with experimental estimates is obtained. We find that J increases substantially as the distance between Cu and apical O is increased. There is an important synergetic effect of the Coulomb interaction, expanding the Cu 3d orbital when an electron hops into this orbital, and the O-Cu hopping, being increased by this orbital expansion (breathing). This is a new ingredient in superexchange models. In a model with a fixed basis, breathing effects can be described as a mixing of 3d and 4d orbitals or as a single 3d → 4d excitation.