Evolution of the spectral lineshape at the magnetic transition in Sr2IrO4 and Sr3Ir2O7

TL;DR

This study investigates how magnetic transitions affect the spectral lineshape in two iridate compounds, revealing different behaviors linked to their magnetic and electronic properties, and compares findings with theoretical models.

Contribution

It provides new insights into the spectral lineshape evolution at magnetic transitions in Sr2IrO4 and Sr3Ir2O7, highlighting differences in coherent and incoherent spectral contributions.

Findings

Spectral weight transfer at TN in Sr3Ir2O7

No spectral lineshape change at TN in Sr2IrO4

Coherent spectral contribution dominates in Sr3Ir2O7

Abstract

Sr2IrO4 and Sr3Ir2O7 form two families of spin-orbit Mott insulators with quite different charge gaps and an antiferromagnetic (AF) ground state. This offers a unique opportunity to study the impact of long-range magnetic order in Mott insulators. It appears to play a different role in the two families, as there is almost no change of the resistivity at the magnetic transition TN in Sr2IrO4 and a large one in Sr3Ir2O7. We use angle-resolved photoemission to study the evolution of the spectral lineshape through the magnetic transition. We use Ru and La substitutions to tune TN and discriminate changes due to temperature from those due to magnetic order. We evidence a shift and a transfer of spectral weight in the gap at TN in Sr3Ir2O7, which is absent in Sr2IrO4. We assign this behavior to a significantly larger coherent contribution to the spectral lineshape in Sr3Ir2O7, which evolves strongly at TN. On the contrary, the Sr2IrO4 lineshape is dominated by the incoherent part, which is insensitive to TN. We compare these findings to theoretical expections of the Slater vs Mott antiferromagnetism within Dynamical Mean Field Theory.