Compositional superlattices based on PtCl/PtBr MX materials

摘要

We consider theoretically a novel class of compositional superlattices consisting of alternating layers of quasi-one-dimensional (QlD) MX (halogen-bridged, transition metal) chain materials. In particular, we have studied a superlattice based on the PtCl/PtBr unit where the Peierls band gap for PtCl is (approximately)2.4 eV and (approximately)1.5 eV for PtBr. We have calculated electronic properties, optical absorption and vibrational properties (e.g. Raman spectrum) of an MX superlattice using a discrete, two-band, tight-binding Peierls-Hubbard model. The electronic band structure reveals a typical subband structure and varies with the relative lengths of the constituent PtCl and PtBr units. The MX superlattice can be thought of as an analog of a GaAs/GaAl(sub x)As(sub 1-x) compositional superlattice but with the added feature that the optical, transport and various other physical properties are modified due to presence of nonlinear excitations (e.g. polarons) in the doped samples.