Spin-orbit-controlled metal-insulator transition in Sr${}_2$IrO${}_4$

Abstract

In the context of correlated insulators, where electron-electron interactions (U) drive the localization of charge carriers, the metal-insulator transition (MIT) is described as either bandwidth (BC) or filling (FC) controlled. Motivated by the challenge of the insulating phase in Sr${}_2$IrO${}_4$, a new class of correlated insulators has been proposed, in which spin-orbit coupling (SOC) is believed to renormalize the bandwidth of the half-filled $j_{\mathrm{eff}}=1/2$ doublet, allowing a modest U to induce a charge-localized phase. Although this framework has been tacitly assumed, a thorough characterization of the ground state has been elusive. Furthermore, direct evidence for the role of SOC in stabilizing the insulating state has not been established, since previous attempts at revealing the role of SOC have been hindered by concurrently occurring changes to the filling. We overcome this challenge by employing multiple substituents that introduce well defined changes to the signatures of SOC and carrier concentration in the electronic structure, as well as a new methodology that allows us to monitor SOC directly. Specifically, we study Sr${}_2$Ir${}_{1-x}$T${}_x$O${}_4$ (T = Ru, Rh) by angle-resolved photoemission spectroscopy (ARPES), combined with ab-initio and supercell tight-binding calculations. This allows us to distinguish relativistic and filling effects, thereby establishing conclusively the central role of SOC in stabilizing the insulating state of Sr${}_2$IrO${}_4$. Most importantly, we estimate the critical value for spin-orbit coupling in this system to be ${\lambda }_c=0.42\pm 0.01$ eV, and provide the first demonstration of a spin-orbit-controlled MIT.

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• Light-induced insulator-metal transition in Sr${}_2$IrO${}_4$ reveals the nature of the insulating ground state
• Spin-phonon interactions and magnetoelectric coupling in Co${}_4$$B_2$O${}_9$ ($B$ = Nb, Ta)
• Origin of the different electronic structure of Rh- and Ru-doped Sr2IrO4
• Strain-induced superconductivity in Sr2IrO4
• Quasi-2D anomalous Hall Mott insulator of topologically engineered Jeff =1/2 electrons
• Soft-Chemical Synthesis, Structure Evolution, and Insulator-to-Metal Transition in a Prototypical Metal Oxide, λ-RhO${}_2$
• Constraints on the two-dimensional pseudo-spin 1/2 Mott insulator description of Sr${}_2$IrO${}_4$
• Reversible modulation of metal-insulator transition in VO2 via chemically-induced oxygen migration
• Mott Gap Softening Coinciding with Spin Correlations Collapse in a-RuCl3
• Metal-insulator transitions in pyrochlore oxides
• (H,Li)${}_6$Ru${}_2$O${}_6$ : a possible zero-field Ru${}^{3+}$-based Kitaev Quantum Spin Liquid
• Quantum Criticality in a Layered Iridate
• Strain tunable electronic ground states in two-dimensional iridate thin films
• Anomalous Fermi pockets on Hund's metal surface of Sr2RuO4 induced by the correlation-enhanced spin-orbit coupling
• The rich phase diagram of the prototypical iridate Ba${}_2$IrO${}_4$: Effective low-energy models and metal-insulator transition
• Anomalous Nodal Gap in a Doped Spin-1/2 Antiferromagnetic Mott Insulator
• Microscopic model realization of $\mathbf{d}$-wave pseudospin current order in Sr${}_2$IrO${}_4$