Evidence for a soft-phonon-mode-driven Peierls-type distortion in Sc$_3$CoC$_4$

TL;DR

This study presents experimental and theoretical evidence that a soft phonon mode induces a Peierls-type structural distortion in the quasi-one-dimensional superconductor Sc$_3$CoC$_4$, involving temperature-dependent phonon-driven atomic displacements.

Contribution

It demonstrates the phonon-softening mechanism driving the Peierls distortion in Sc$_3$CoC$_4$, highlighting the role of low-dimensionality and anisotropic correlations.

Findings

Identification of a phonon-softening mechanism causing structural distortion.

Observation of an intermediate temperature regime with dynamic atom displacements.

Evidence of highly anisotropic correlation lengths in the distorted phase.

Abstract

We provide experimental and theoretical evidence for the realization of the Peierls-type structurally distorted state in the quasi-one-dimensional superconductor Sc$_3$CoC$_4$ by a phonon-softening mechanism. The transition from the high- to the final low-temperature phase below 80K proceeds via an extended intermediate temperature regime between 80K and 150K characterized by phonon-driven atom displacements. In support of the low-dimensional character of the title compound we find a highly anisotropic correlation-length of these dynamic distortions.