Abstract
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 insulator phase.
| Original language | English |
|---|---|
| Article number | 913 |
| Journal | Nature Communications |
| Volume | 13 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 2022 |
Funding
We thank D.F. McMorrow, B. Normand, Ch. Rüegg, and J.P. Hill for fruitful discussions. Work performed at Brookhaven National Laboratory was supported by the US Department of Energy, Division of Materials Science, under Contract No. DE-SC0012704. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. This research used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725. D.G.M. acknowledges support from the Swiss National Science Foundation, Fellowship No. P2EZP2_175092. H.S. acknowledges support from JSPS KAKENHI Grant No. JP19K14650. X.L. acknowledges the support from the National Natural Science Foundation of China under grant No. 11934017. K.J. and Y.G.S. acknowledge the support from the National Natural Science Foundation of China (Grants No. U2032204), and the K.C. Wong Education Foundation (GJTD-2018-01). Y.G.S. acknowledges the Chinese National Key Research and Development Program (No. 2017YFA0302901) and the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB33000000). J.L. acknowledges support from the National Science Foundation under Grant No. DMR-1848269. J.Y. acknowledges funding from the State of Tennessee and Tennessee Higher Education Commission (THEC) through their support of the Center for Materials Processing. H.M. was sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy.