Effects of structural ordering on infrared active vibrations within Bi2(Te(1-x)Sex)3

We performed a materials investigation into the properties of the THz conductivity spectra in the ternary alloy Bi2(Te(1-x)Sex)3 as a function of selenium fraction, x, and temperature. We find that the reduction in crystalline anharmonicity caused by the preferential ordering of the x = 1/3 phase of Bi2(Te(1-x)Sex)3 results in the prominent Eu1 phonon (occurring between 1.5 and 1.9 THz) red-shifting on cooling less than the binary Bi2Te3 and Bi2Se3 samples. We also find that the Eu1 phonon couples to an electronic continuum at low temperatures (T 40 K), regardless of Bi2(Te(1-x)Sex)3 stoichiometry or the Hall mobility of the topological insulator crystal. These results highlight the role that these optical modes play in the electronic and thermal transport within this ternary alloy and pave the way for exploring the interesting phonon dynamics within these topological insulator and thermoelectric materials.

Automated summary

In this study, we investigated the properties of THz conductivity spectra in the ternary alloy Bi2(Te(1-x)Sex)3 as a function of selenium fraction, x, and temperature. Our findings suggest that preferential ordering in the x = 1/3 phase of Bi2(Te(1-x)Sex)3 leads to a red-shift in the Eu1 phonon on cooling, compared to binary Bi2Te3 and Bi2Se3 samples. We also observed coupling between the Eu1 phonon and an electronic continuum at low temperatures, regardless of the alloy's stoichiometry or the Hall mobility of the topological insulator crystal. These results highlight the importance of these optical modes in the transport properties of this ternary alloy.