Low-energy phonons and superconductivity in Sn$_{0.8}$In$_{0.2}$Te

TL;DR

This study investigates low-energy phonons in superconducting Sn$_{0.8}$In$_{0.2}$Te using neutron scattering, revealing phonon behavior near the superconducting transition without significant changes across the transition.

Contribution

First neutron scattering measurements of low-energy phonons in Sn$_{0.8}$In$_{0.2}$Te, providing insights into phonon dynamics related to its superconductivity.

Findings

Transverse phonons have substantial energy width at energies near twice the superconducting gap.

No observable change in phonon energy width between superconducting and normal states.

The crystal structure remains well ordered with no signs of instability.

Abstract

We present neutron scattering measurements on low-energy phonons from a superconducting ($T_{c} = 2.7$~K) Sn$_{0.8}$In$_{0.2}$Te single crystal sample. The longitudinal acoustic phonon mode and one transverse acoustic branch have been mapped out around the (002) Bragg peak for temperatures of 1.7 K and 4.2 K. We observe a substantial energy width of the transverse phonons at energies comparable to twice the superconducting gap; however, there is no change in this width between the superconducting and normal states. We also confirm that the compound is well ordered, with no indications of structural instability.