Electronic properties of the ordered (√2 × √2) superlattice phases La2Cu0.5Li0.5O4 and La2Au0.5Li0.5O4

Abstract Linear augmented-plane-wave band-structure results for La 2 Cu 0.5 Li 0.5 O 4 , an ordered Cu 3+ -Li + superlattice phase that can be formed via Li → Cu substitution within the CuO 2 layers of La 2 CuO 4 , predict that this compound is an ordinary band semiconductor with cluster-like features near E F . The calculated semiconductor gap of ∼ 0.7 eV separates a narrow (∼ 0.4 eV) filled d 3 z 2 − r 2 level from a broader (∼ 1 eV unoccupied d x 2 − y 2 subband. Although a low-lying La 5d band eliminates the corresponding gap in isostructural La 2 Au 0.5 Li 0.5 O 4 , semiconducting properties would be restored if the recently proposed T′ structure proves to be correct. Electron or hole doping of these cluster-type materials should yield interesting transport properties, including possible superconductivity.