Vibronic order and emergent magnetism in cubic $d^1$ double perovskites

TL;DR

This paper explores how spin-orbit and vibronic couplings in cubic $d^1$ double perovskites lead to a novel entangled state with dynamic vibronic order, explaining previously unexplained experimental phenomena.

Contribution

It introduces the concept of spin-orbit-lattice entanglement and dynamic vibronic order in $d^1$ double perovskites, advancing understanding of their magnetic phases.

Findings

Magnetic ordered states coexist with dynamic vibronic order.

Vibronic quadrupole moments are ordered on sites.

The model explains previously unexplained experimental features.

Abstract

The synergistic interplay of different interactions in materials leads to the emergence of novel quantum phenomena. Spin-orbit and vibronic couplings usually counteract each other, however, in cubic $d^1$ double perovskites they coexist and give rise to spin-orbit-lattice entanglement with unquenched dynamic Jahn-Teller effect on the metal sites. The correlation of these entangled states induced by intersite interactions was not assessed so far. Here, we investigate the joint cooperative effect of spin-orbit and vibronic interactions on the formation of the ordered phases in $d^1$ double perovskites. We found that the magnetic ordered states in these systems coexist with a dynamic vibronic order characterized by the ordering of vibronic quadrupole moments on sites. This treatment allows the rationalization of a number of unexplained features of experimentally investigated phases.