Jahn-Teller Effect in Systems with Strong On-Site Spin-Orbit Coupling

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Strong spin-orbit coupling (SOC) typically suppresses orbital degeneracy.
• The Jahn-Teller (JT) effect is known to distort lattices in response to orbital degeneracy.
• The interplay between SOC and JT effects in iridates' t_{2g} manifold is not fully understood.

Purpose of the Study:

• To investigate the influence of the Jahn-Teller mechanism on spin-orbit excitons in iridates.
• To reconcile the apparent ineffectiveness of the JT effect with observed phenomena in iridate spectroscopy.
• To explain peculiar features in resonant inelastic x-ray scattering (RIXS) spectra of Sr$_{2}$IrO$_{4}$.

Main Methods:

• Theoretical analysis of the t_{2g} electronic manifold in iridates under strong spin-orbit coupling.
• Modeling the Jahn-Teller effect's interaction with spin-orbit excitons.
• Comparison of theoretical predictions with experimental RIXS data for Sr$_{2}$IrO$_{4}$.

Main Results:

• The Jahn-Teller effect does not alter the j$_{eff}$=1/2 antiferromagnetic ground state.
• Distinctive signatures are observed in the j$_{eff}$=3/2 spin-orbit exciton due to JT coupling.
• The JT mechanism facilitates the hopping of spin-orbit excitons between nearest-neighbor sites without creating defects.
• This hopping is insensitive to the phase of the wave function defining isospin, unlike purely electronic propagation.

Conclusions:

• The Jahn-Teller effect remains relevant in iridates despite strong spin-orbit coupling.
• JT coupling provides a mechanism for spin-orbit exciton dynamics.
• This framework explains anomalous features in RIXS spectra of Sr$_{2}$IrO$_{4}$, highlighting the coupled nature of electronic, spin, and lattice degrees of freedom.