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
Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY, 11973, USA.
Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232, Villigen, Switzerland.
Nat Commun. 2022 Feb 17;13(1):913. doi: 10.1038/s41467-022-28207-w.
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 SrIrO. 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 SrIrO indicating that this material is a realization of the long-predicted antiferromagnetic excitonic insulator phase.
激子绝缘体通常被认为是通过束缚电子 - 空穴对的软电荷模式凝聚形成的。然而，这假定软激子具有自旋单重态特征。早期的理论研究也预测了一种非常不同的情况，即磁激子的凝聚会导致反铁磁激子绝缘体态。在此，我们报告了对SrIrO的共振非弹性X射线散射（RIXS）测量结果。通过分离光谱的纵向分量，我们识别出一种磁模式，它在磁和结构布里渊区中心定义明确，但在这些高对称点之间与电子连续体合并，并且在加热时随着材料电阻率的降低而衰减。我们表明，一种双层哈伯德模型，其中电子 - 空穴对通过交换相互作用束缚在一起，能够一致地解释SrIrO的所有电子和磁特性，表明这种材料是长期预测的反铁磁激子绝缘相的一种实现。
