Displacement Waves in La₂CuO_4-δ and La_1.85Sr_0.15CuO_4-δ

Abstract

Structural investigation of orthorhombic La 2 CuO 4-δ and La 1.85 Sr 0.15 CuO 4-δ was carried out by means of X-ray and neutron diffraction on the basis of the space group Cmmm. The periodic expansion/contraction type distortion of CuO 6 octahedra was found in both orthorhombic compounds. The distortion is nearly one-dimensional in La 2 CuO 4-δ but is two-dimensional in La 1.85 Sr 0.15 CuO 4-δ . The existence of a charge-density wave, CDW, with a wave vector q CDW =(0 0 c * ) is highly possible in the structures.