An investigation of the optical properties of the misfit layer compound (PbSe)_1+δ(NbSe₂)_n

Misfit layer compounds (MLCs) consist of two sublattices that have at least one differing lattice parameter. The incommensurate structure and composite nature enables the simultaneous presence of contradictory properties such as low thermal conductivity alongside high electrical conductivity, making them ideal candidates for thermoelectic materials [1]. The general structure of a MLCs is (MX)_1+δ(TX₂)_n, where MX is a rock salt (M = Sn, Pb, Bi, rare earth; X = S, Se) and TX₂ is a transition metal dichalcogenide (T = Ti, V, Nb, Ta, Cr; X = S, Se). The misfit parameter, δ, describes the ratio between the lattice parameters along the crystallographic a axis, while n describes the number of TX₂ layers in between MX layers [2]. (PbSe)_1+δ(NbSe₂)_n is a MLC composed of semiconductor (PbSe) and superconducting transition metal dichalcogenide (NbSe₂). Single crystal samples were synthesized and characterized by x-ray diffraction and ac-resistivity. The optical reflectance of (PbSe)_1+δ(NbSe₂)_n will be presented with the aim of investigating how the optical properties change as NbSe₂ layers are added.
[1] D.R. Merrill, et al. Materials, 8:2000, 2015.
[2] G.A. Wiegers. Prog. Solid St. Chem, 24:1, 1996.