Magnetization dynamics fingerprints of an excitonic condensate $t_{2g}^4$ magnet

Abstract

The competition between spin-orbit coupling $\lambda$ and electron-electron interaction $U$ leads to a plethora of novel states of matter, extensively studied in the context of $t_{2g}^4$ and $t_{2g}^5$ materials, such as ruthenates and iridates. Excitonic magnets -- the antiferromagnetic state of bounded electron-hole pairs -- is a prominent example of phenomena driven by those competing energy scales. Interestingly, recent theoretical studies predicted that excitonic magnets can be found in the ground-state of spin-orbit-coupled $t_{2g}^4$ Hubbard models. Here, we present a detailed computational study of the magnetic excitations in that excitonic magnet, employing one-dimensional chains (via density matrix renormalization group) and small two-dimensional clusters (via Lanczos). Specifically, first we show that the low-energy spectrum is dominated by a dispersive (acoustic) magnonic mode, with extra features arising from the $\lambda =0$ state in the phase diagram. Second, and more importantly, we found a novel magnetic excitation forming a high-energy optical mode with the highest intensity at wavevector $q\to 0$. In the excitonic condensation regime at large $U$, we also have found a novel high-energy $\pi$-mode composed solely of orbital excitations. These unique fingerprints of the $t_{2g}^4$ excitonic magnet are important in the analysis of neutron and RIXS experiments.

References in corpus (23)

• Novel Jeff = 1/2 Mott State Induced by Relativistic Spin-Orbit Coupling in Sr2IrO4
• Excitonic quasiparticles in a spin-orbit Mott insulator
• Spectral Functions with the Density Matrix Renormalization Group: Krylov-space Approach for Correction Vectors
• Neutron and ARPES Constraints on the Couplings of the Multiorbital Hubbard Model for the Pnictides
• Effective magnetic interactions in spin-orbit coupled $d^4$ Mott insulators
• Observation of spin-orbit excitations and Hund's multiplets in Ca${}_2$RuO${}_4$
• J-freezing and Hund's rules in spin-orbit-coupled multiorbital Hubbard models
• Magnetic Excitations in Spin-Orbit Coupled $d^4$ Mott Insulator on Square Lattice
• Magnetism out of disorder in a J=0 compound Ba2YIrO6
• Orbital-selective Peierls phase in the metallic dimerized chain MoOCl${}_2$
• Hopping induced ground-state magnetism in 6H perovskite iridates
• Engineering One-Dimensional Quantum Stripes from Superlattices of Two-Dimensional Layered Materials
• Diluted paramagnetic impurities in nonmagnetic Ba${}_2$YIrO${}_6$
• Density matrix renormalization group study of a three-orbital Hubbard model with spin-orbit coupling in one dimension
• Magnetic states of quasi-one-dimensional iron chalcogenide Ba${}_2$FeS${}_3$
• Block orbital-selective Mott insulators: a spin excitation analysis
• Prediction of exotic magnetic states in the alkali metal quasi-one-dimensional iron selenide compound Na${}_2$FeSe${}_2$
• Spin-orbit effects in pentavalent Iridates: Models and materials
• Quantum magnetism of iron-based ladders: Blocks, spirals, and spin flux
• Suppression of effective spin-orbit coupling by thermal fluctuations in spin-orbit coupled antiferromagnets
• Intertwined charge, spin, and pairing orders in doped iron ladders
• Novel Block Excitonic Condensate at $n=3.5$ in a Spin-Orbit Coupled $t_{2g}$ Multiorbital Hubbard Model
• Magnetic phases for two $t_{2g}$ holes with spin-orbit coupling and crystal field

Cited by in corpus (5)

• Electronic excitations in $5d^4$ J=0 Os${}^{4+}$ halides studied by RIXS and optical spectroscopy
• Spin-orbit coupling in a half-filled $t_{2g}$ shell: the case of $5d^3$ K${}_2$ReCl${}_6$
• Electronic structure, magnetic properties and pairing tendencies of the copper-based honeycomb lattice Na${}_2$Cu${}_2$TeO${}_6$
• J = 0 nonmagnetic insulating state in K${}_2$Os$X_6$ (X = F, Cl and Br)
• Quasimolecular electronic structure of the trimer iridate Ba${}_4$NbIr${}_3$O${}_{12}$