Impact of anisotropic interactions on cubic Eg quadrupole orders
Multipole degrees of freedom and their orders in strongly correlated electron systems have attracted growing interest in recent years. In several cubic Pr-based f-electron systems with two f electrons per a Pr ion, it is reported that they possess non-Kramers doublet crystalline-electric field ground state with Eg quadrupole and Txyz type octuple moments. They show various quadrupole orders, non-Fermi liquids, superconductivity, and many interesting low temperature properties .
In this study, we analyze a model with non-Heisenberg (non-XY type) anisotropic interactions present in the real quadrupole systems. We find that their effects are drastic and even qualitative changes emerge in their ordered phases. In this talk, first we show results of mean-field analysis for interacting quadrupole moments in a cubic fcc lattice . We demonstrate that novel partial ordered states at high temperature are generally realized rather than a simple quadrupole order with a single wave number. In the second part, we analyze a “double transition” observed in PrV2Al20, which is expected to be triggered by the ferro Txyz octuploe order . We propose a simple scenario for the double transition when the anisotropic quadrupole interactions in addition to simple octupole-octupole one are taken into account . The magnetic-field vs temperature phase diagrams are also examined and several field-induced phases are proposed for the field directions , , and . T. Onimaru and H. Kusunose, J. Phys. Soc. Jan. 85, 082002 (2016).
 H. Tsunetsugu, T. Ishitobi, and KH, arXiv.2102.06346.
 A. Sakai et al., unpublished; A. S. Patri et al., Nat. Comm. 10, 4092 (2019).
 T. Ishitobi and KH, unpublished.