Antiferromagnetic excitonic insulator state in Sr3Ir2O7

Journal Article · 17 February 2022 · Nature Communications

DOI: https://doi.org/10.1038/s41467-022-28207-w · OSTI ID:1845606

Mazzone, D. G. ; Shen, Y.; Suwa, H. ; Fabbris, G. ; Yang, J.; Zhang, S. -S.; Miao, H. ; Sears, J.; Jia, Ke; Shi, Y. G.; Upton, M. H.; Casa, D. M.; Liu, X.; Liu, Jian ; Batista, C. D. ; Dean, M. P. M.

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 Sr ₃ Ir ₂ O ₇ . 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 Sr ₃ Ir ₂ O ₇ indicating that this material is a realization of the long-predicted antiferromagnetic excitonic insulator phase.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: Chinese Academy of Sciences; Chinese Academy of Sciences (CAS) - Strategic Priority Research Program; Chinese National Key Research and Development Program; JSPS KAKENHI; Japan Society for the Promotion of Science (JSPS) - KAKENHI; K.C. Wong Education Foundation; National Key Research and Development Program of China; National Natural Science Foundation of China; National Natural Science Foundation of China (NSFC); National Science Foundation (NSF); Swiss National Science Foundation; Swiss National Science Foundation (SNSF); Tennessee Higher Education Commission (THEC); USDOE; USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division
• Grant/Contract Number: AC02-06CH11357; AC05-00OR22725; SC0012704
• OSTI ID: 1845606
• Report Number(s): BNL-222896-2022-JAAM; 913; PII: 28207
• Journal Information: Nature Communications, Journal Name: Nature Communications Journal Issue: 1 Vol. 13; ISSN 2041-1723
• Publisher: Nature Publishing GroupCopyright Statement
• Country of Publication: United Kingdom
• Language: English