Lattice frustration in spin-orbit Mott insulator Sr3Ir2O7 at high pressure

TL;DR

This study investigates how high pressure affects the magnetic and structural properties of the spin-orbit Mott insulator Sr3Ir2O7, revealing a pressure-induced magnetic transition linked to lattice frustration without an insulator-metal transition.

Contribution

It demonstrates the critical role of lattice frustration and octahedral tilting in pressure-induced phase transitions in Sr3Ir2O7, highlighting the importance of lattice geometry in its magnetic behavior.

Findings

Magnetic and structural transition at 14.4 GPa

No insulator-metal transition observed

Lattice frustration influences high-pressure phases

Abstract

The intertwined charge, spin, orbital, and lattice degrees of freedom could endow 5d compounds with exotic properties. Current interest is focused on electromagnetic interactions in these materials, whereas the important role of lattice geometry remains to be fully recognized. For this sake, we investigate pressure-induced phase transitions in the spin-orbit Mott insulator Sr3Ir2O7 with Raman, electrical resistance, and x-ray diffraction measurements. We reveal an interesting magnetic transition coinciding with a structural transition at 14.4 GPa, but without a concurrent insulator-metal transition. The conventional correlation between magnetic and Mott insulating states is thereby absent. The observed softening of the one-magnon mode can be explained by a reduced tetragonal distortion, while the actual magnetic transition is associated with tilting of the IrO6 octahedra. This work highlights the critical role of lattice frustration in determining the high-pressure phases of Sr3Ir2O7. The ability to control electromagnetic properties via manipulating the crystal structure with pressure promises a new way to explore new quantum states in spin-orbit Mott insulators.