Plotnikova Ekaterina M, Daghofer Maria, van den Brink Jeroen, Wohlfeld Krzysztof
Institute for Theoretical Solid State Physics, IFW Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany.
Institute for Functional Materials and Quantum Technologies, University of Stuttgart, Pfaffenwaldring 57 D-70550 Stuttgart, Germany.
Phys Rev Lett. 2016 Mar 11;116(10):106401. doi: 10.1103/PhysRevLett.116.106401. Epub 2016 Mar 7.
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}.
当强自旋轨道耦合消除轨道简并时，同时似乎会使 Jahn - Teller 机制失效。我们讨论这种情况，即铱酸盐的(t_{2g})多重态，并表明，虽然 Jahn - Teller 效应确实不影响(j_{eff}=1/2)反铁磁有序基态，但它在(j_{eff}=3/2)自旋轨道激子中导致独特的特征。它允许自旋轨道激子在最近邻位点之间跳跃，而不会在(j_{eff}=1/2)反铁磁体中产生缺陷。这是因为晶格驱动的 Jahn - Teller 机制仅与轨道自由度耦合，而对定义同位旋(j_{z})的波函数相位不敏感。这与纯电子传播形成鲜明对比，纯电子传播会守恒同位旋，Jahn - Teller 耦合的存在可以解释(Sr_{2}IrO_{4})的测量共振非弹性 X 射线散射光谱的一些奇特特征。
