title: Jahn-Teller Effect in Systems with Strong On-Site Spin-Orbit Coupling.
abstract: When strong spin-orbit coupling removes orbital degeneracy, it would at the same time appear to render the Jahn-Teller mechanism ineffective. We discuss such a situation, the t_{2g} manifold of iridates, and show that, while the Jahn-Teller effect does indeed not affect the j_{eff}=1/2 antiferromagnetically ordered ground state, it leads to distinctive signatures in the j_{eff}=3/2 spin-orbit exciton. It allows for a hopping of the spin-orbit exciton between the nearest-neighbor sites without producing defects in the j_{eff}=1/2 antiferromagnet. This arises because the lattice-driven Jahn-Teller mechanism only couples to the orbital degree of freedom but is not sensitive to the phase of the wave function that defines isospin j_{z}. This contrasts sharply with purely electronic propagation, which conserves isospin, and the presence of Jahn-Teller coupling can explain some of the peculiar features of measured resonant inelastic x-ray scattering spectra of Sr_{2}IrO_{4}.
authors.affiliation: Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany.
authors.forename: Ekaterina M
authors.initials: EM
authors.lastname: Plotnikova
authors.affiliation: Institute for Functional Materials and Quantum Technologies, University of Stuttgart, Pfaffenwaldring 57 D-70550 Stuttgart, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Daghofer
authors.affiliation: Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany.|Institute for Theoretical Physics, TU Dresden, 01069 Dresden, Germany.|Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Jeroen
authors.initials: J
authors.lastname: van den Brink
authors.affiliation: Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University, 2575 Sand Hill Road, Menlo Park, California 94025, USA.|Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, PL-02093 Warsaw, Poland.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Wohlfeld