BAND PICTURE OF THE SPIN-PEIERLS TRANSITION IN THE SPIN-1/2 LINEAR-CHAIN CUPRATE GECUO3

The results of electronic-structure calculations for GeCUO3 feature a pair of narrow (approximately 1 eV) half-filled, one-dimensional sigma* conduction bands that originate from two edge-sharing CuO2 linear chains in the orthorhombic cell. Unusual transport properties are predicted since the confined carrier motion along the chains (at any band filling) requires tunneling through nodal charge-density regions. At the spin-Peierls transition, the dimerization of the CuO2 chains can open a band gap at E(F), provided that the Cu displacements in neighboring chains are staggered.