Department of Physics, New York University, New York, NY, 10003, USA.
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
Nat Commun. 2019 Feb 7;10(1):644. doi: 10.1038/s41467-019-08497-3.
Uranium compounds can manifest a wide range of fascinating many-body phenomena, and are often thought to be poised at a crossover between localized and itinerant regimes for 5f electrons. The antiferromagnetic dipnictide USb has been of recent interest due to the discovery of rich proximate phase diagrams and unusual quantum coherence phenomena. Here, linear-dichroic X-ray absorption and elastic neutron scattering are used to characterize electronic symmetries on uranium in USb and isostructural UBi. Of these two materials, only USb is found to enable strong Hund's rule alignment of local magnetic degrees of freedom, and to undergo distinctive changes in local atomic multiplet symmetry across the magnetic phase transition. Theoretical analysis reveals that these and other anomalous properties of the material may be understood by attributing it as the first known high temperature realization of a singlet ground state magnet, in which magnetism occurs through a process that resembles exciton condensation.
铀化合物可以表现出广泛的迷人多体现象，通常被认为处于 5f 电子局域和巡游态之间的交叉点。由于发现了丰富的近邻相图和不寻常的量子相干现象，反铁磁的二价金属 USb 最近引起了人们的兴趣。在这里，线性二向色性 X 射线吸收和弹性中子散射被用于表征 USb 和同构 UBi 中铀的电子对称性。在这两种材料中，只有 USb 被发现能够使局部磁自由度强烈遵循亨德规则排列，并在磁相变过程中经历局部原子多重态对称性的显著变化。理论分析表明，通过将其归因于首个已知的高温单重态磁体实现，可以理解材料的这些和其他异常性质，其中通过类似于激子凝聚的过程产生磁性。
