Pressure effect on the energy structure and superexchange interaction in undoped orthorhombic La2CuO4

摘要

We studied the pressure dependences of the electronic structure and superexchange interaction J(P) = J(A) - J(B) (where JA and JB are antiferromagnetic (AFM) and ferromagnetic (FM) contributions) in antiferromagnetic La214 under hydrostatic, uniaxial (along c-axial) 3% compressions and 1% in-plane compressions by the local density approximation with generalized tight-binding method (LDA + GTB cell approach). The changes in J(P) correlated with the experimentally known T-C(P) dependence are in accordance with the relation dT(C)/dP = (partial derivative T-C/partial derivative J)(partial derivative J/partial derivative P), where partial derivative T-C/partial derivative J similar to 0.1. The in-plane pressure more effectively stabilizes the ground singlet two-hole state A(1) than the simple hydrostatic pressure, its effect on J and T-C is the largest. Within the same cell approach together with the superexchange interaction J(P), the valence band structure was calculated. Its changes with pressure clearly reproduce the k-distribution of the singlet and triplet quasi-particles over the Brillouin zone (BZ).