Emergent Orbital Correlations and the Hidden Role of Jahn-Teller Physics in Spin-Orbit Coupled Systems

In transition metal oxides with partially filled d-orbitals, the competition between spin-orbit coupling (SOC), electron correlations, and Jahn-Teller (JT) interactions gives rise to a rich and complex energy landscape. This interplay can stabilize a variety of exotic quantum phases, including spin-orbit Mott insulators, quantum spin liquids, and excitonic magnets, which are of fundamental interest for quantum science. In 4d and 5d systems, like iridates or ruthenates, strong SOC is widely believed to fully lift orbital degeneracies, suppressing JT distortions and freezing orbital dynamics. However, recent theoretical advances challenge this conventional wisdom, revealing that JT physics can persist in a dynamic form even in the presence of strong SOC.

In this seminar, we present a framework that incorporates SOC, JT coupling, and intersite electronic hybridization—an intrinsic feature of all solids. We show that band hybridization can restore local orbital polarization otherwise quenched by SOC, giving rise to robust but short-ranged orbital correlations [1]. This emergent cooperative effect exposes a latent JT instability, offering new insights into the nature of spin-orbital excitations. Finally, we turn to 3d systems such as Mn³⁺, where JT interactions dominate over SOC. Remarkably, even in this regime, strong spin-orbit entanglement emerges via JT-induced t₂_g–e_g mixing [2, 3], highlighting the pervasive and often underestimated influence of SOC across different electronic environments.

[1] A.S. Miñarro, G. Herranz, Emergent Orbital Correlations in Strongly Spin-Orbit Coupled Systems, submitted

[2] A.S. Miñarro, G. Herranz Phys. Rev. B 106, 165108 (2022)

[3] A.S. Miñarro et al., Spin-orbit entanglement driven by the Jahn-Teller effect. Nat Commun 15, 8694 (2024)