Specifics of the Elemental Excitations in "True One-Dimensional" MoI$_3$ van der Waals Nanowires

TL;DR

This study investigates the temperature-dependent Raman spectra of MoI$_3$, a one-dimensional van der Waals material, revealing a magnetic phase transition and providing insights into its phononic and magnonic states relevant for spintronics.

Contribution

It offers the first detailed analysis of the magnetic and vibrational properties of MoI$_3$, highlighting its potential for spintronic applications and understanding of one-dimensional magnetic systems.

Findings

Evidence of a magnetic phase transition from Raman data

MoI$_3$ is an easy-plane antiferromagnet with helical inter-chain spin order

Theoretical phonon and magnon frequencies match experimental observations

Abstract

We report on the temperature evolution of the polarization-dependent Raman spectrum of exfoliated MoI$_3$, a van der Waals material with a "true one-dimensional" crystal structure that can be exfoliated to individual atomic chains. The temperature evolution of several Raman features reveals anomalous behavior suggesting a phase transition of a magnetic origin. Theoretical considerations indicate that MoI$_3$ is an easy-plane antiferromagnet with alternating spins along the dimerized chains and with inter-chain helical spin ordering. The calculated frequencies of the phonons and magnons are consistent with the interpretation of the experimental Raman data. The obtained results shed light on the specifics of the phononic and magnonic states in MoI$_3$ and provide a strong motivation for future study of this unique material with potential for spintronic device applications.