Excitonic insulators are usually considered to form via the condensation of a soft charge mode of bound electron-hole pairs. This, however, presumes that the soft exciton is of spin-singlet character. Early theoretical considerations have also predicted a very distinct scenario, in which the condensation of magnetic excitons results in an antiferromagnetic excitonic insulator state. Here we report resonant inelastic x-ray scattering (RIXS) measurements of Sr3Ir2O7. By isolating the longitudinal component of the spectra, we identify a magnetic mode that is well-defined at the magnetic and structural Brillouin zone centers, but which merges with the electronic continuum in between these high-symmetry points and which decays upon heating concurrent with a decrease in the material's resistivity. We show that a bilayer Hubbard model, in which electron-hole pairs are bound by exchange interactions, consistently explains all the electronic and magnetic properties of Sr3Ir2O7 indicating that this material is a realization of the long-predicted antiferromagnetic excitonic insulators phase.
@article{arxiv.2201.04030,
title = {Antiferromagnetic Excitonic Insulator State in Sr3Ir2O7},
author = {D. G. Mazzone and Y. Shen and H. Suwa and G. Fabbris and J. Yang and S-S. Zhang and H. Miao and J. Sears and Ke Jia and Y. G. Shi and M. H. Upton and D. M. Casa and X. Liu and J. Liu and C. D. Batista and M. P. M. Dean},
journal= {arXiv preprint arXiv:2201.04030},
year = {2022}
}
Comments
accepted in Nature Communications; 6 pages main materials