Giant spin-phonon-electronic coupling in a 5d oxide

TL;DR

This paper reports a giant spin-phonon-electronic coupling in the 5d oxide NaOsO3, revealing unprecedented interactions that influence its metal-insulator transition and offering new insights into 5d material behavior.

Contribution

It demonstrates the largest measured spin-phonon frequency shift in a 5d oxide and links it to the large spatial extent of 5d orbitals, advancing understanding of coupled phenomena.

Findings

Largest spin-phonon frequency shift of 40 cm-1 observed

Identification of octahedral breathing mode linked to spin order

Dynamic charge disproportionation related to metal-insulator transition

Abstract

Enhanced coupling of material properties offers new fundamental insights and routes to multifunctional devices. In this context 5d oxides provide new paradigms of cooperative interactions driving novel emergent behavior. This is exemplified in 5d osmates that host a metal-insulator transition (MIT) driven by magnetic order. Here we consider the most robust case, the 5d perovskite NaOsO3, and reveal a giant coupling between spin and phonon through a frequency shift of {\Delta}{\omega}=40 cm-1, the largest measured in any material. We identify the dominant octahedral breathing mode and show isosymmetry with spin ordering which induces dynamic charge disproportionation that sheds new light on the MIT. The occurrence of the dramatic spin-phonon-electronic coupling in NaOsO3 is due to a property common to all 5d materials: the large spatial extent of the 5d ion. This allows magnetism to couple to phonons on an unprecedented scale and consequently offers multiple new routes to enhanced coupled phenomena.