In electronic solids with strong spin-orbit interactions (SOIs), the spin and orbital degrees of freedom of an electron are quantum mechanically entangled, which may result in an exotic multipolar order instead of a conventional dipolar order such as a magnetic order. Such a higher-degree order is called "hidden order" because of difficulties in experimental detection. Moreover, the number of candidate compounds is limited, especially rare in d electron systems, in which an interplay between SOIs and Coulomb interactions is expected to cause rich physics. Here, we employ state-of-the-art synchrotron X-ray diffraction techniques on a high-quality single crystal to probe subtle symmetry breaking induced by a multipolar order. We unequivocally demonstrate that the double-perovskite Ba2MgReO6 exhibits successive transitions to quadrupolar and then dipolar orders upon cooling, which is consistent with a theory considering SOIs. Our findings are a significant step towards understanding the intriguing physics of multipoles realized by spin-orbit-entangled 5d electrons.
Cite
@article{arxiv.2004.13928,
title = {Detection of multipolar orders in the spin-orbit-entangled 5d Mott insulator Ba2MgReO6},
author = {Daigorou Hirai and Hajime Sagayama and Shang Gao and Hiroyuki Ohsumi and Gang Chen and Taka-hisa Arima and Zenji Hiroi},
journal= {arXiv preprint arXiv:2004.13928},
year = {2020}
}
Comments
17 pages main text, 7 pages supplement, to be published in Phys. Rev. Research