Carrier dynamics in doped bilayer iridates near magnetic quantum criticality

TL;DR

This paper investigates how doping and spin-orbit coupling affect carrier dynamics and Fermi surface topology in bilayer iridates near magnetic quantum criticality, aligning theoretical predictions with experimental findings.

Contribution

It introduces a combined theoretical approach to model doped bilayer iridates, revealing the emergence of small double electron pockets due to octahedral rotation and spin-orbit effects.

Findings

Fermi surface features match experimental observations of small electron pockets.

Spin-orbit coupling shifts the quantum critical point in the phase diagram.

Carrier dispersion calculated using self-consistent methods.

Abstract

Motivated by experiments on the carrier-doped bilayer iridate $(\text{Sr}_{1-x}\text{La}_x)_3\text{Ir}_2\text{O}_7$, we study the dynamics of a single doped electron in a bilayer magnet in the presence of spin-orbit coupling, taking into account the spatially staggered rotation of IrO$_6$ octahedra. We employ an effective single-orbital bilayer $t$-$J$ model, concentrating on the quantum paramagnetic phase near the magnetic quantum critical point. We determine the carrier dispersion using a combination of self-consistent Born and bond-operator techniques. Extrapolating to finite small carrier density we find that, for experimentally relevant parameters, the combination of octahedral rotation and spin-orbit coupling induces a band folding which results in a Fermi surface of small double electron pockets, in striking agreement with experimental observations. We also determine the influence of spin-orbit coupling on the location of the quantum critical point in the undoped case, and discuss aspects of the global phase diagram of doped bilayer Mott insulators.