Atomic and inter-atomic orbital magnetization induced in SrTiO$_3$ by chiral phonons

TL;DR

This paper models how chiral phonons induce large transient magnetization in SrTiO3 through atomic and inter-atomic electronic contributions, advancing understanding of ultrafast magnetization control.

Contribution

It introduces a minimal molecular orbital model revealing atomic and inter-atomic electronic effects responsible for phonon-induced magnetization in SrTiO3.

Findings

Atomic orbital contribution from Ti orbital angular momentum

Inter-atomic circulating current around oxygen atoms

Efficient phonon dressing by electron dynamics

Abstract

An unexpectedly large transient magnetization induced by circularly polarized ferroelectric phonons was recently observed in a nonmagnetic insulator SrTiO3 [Nature 628, 534 (2024)]. We use a minimal molecular orbital model to demonstrate two electronic contributions to this effect. An atomic orbital contribution arises from the pumping of orbital angular momentum of Ti by chiral motion of coordinating oxygen atoms. An additional inter-atomic contribution is associated with the transient circulating current around the oxygen atoms, resulting in efficient dressing of phonons by electron dynamics. The insights provided by our model may facilitate the development of ultrafast magnetization control and orbitronic sources.