Specific features of the properties of lattice vibrations in the Cd$_{1-y}$Hg$_y$Te alloy formed by the CdTe semiconductor and the HgTe semimetal

The specific features of the properties of Hg–Te lattice vibrations have been considered within the percolation model of a mixed Cd$_{1-y}$Hg$_y$Te crystal (alloy), in which the composite medium is formed by the alloy regions enriched in HgTe and CdTe with different Hg-Te vibrational states and, hence, with different characteristics of vibrational modes (frequency and damping parameter). In the HgTe-enriched alloy, the properties of Hg–Te lattice vibrations are determined by a double-well lattice potential for the Hg atom with the off-center localization at low temperatures. In the CdTe-enriched alloys, the properties of Hg–Te lattice vibrations are determined by a single-well lattice potential for the Hg atom in the center of the anion tetrahedron, and the Hg–Te vibrational states are localized. For the HgTe-enriched alloy, the Hg–Te vibrational states are extended. In the percolation scheme of the transformation of the vibrational spectrum of the Cd$_{1-y}$Hg$_y$Te alloy with the composition y, the "137 cm$^{-1}$" mode is a split-off mode of Hg–Te vibrations, or one of the modes of the percolation doublet of HgTe-like vibrations.