Cluster multipole expansion for local symmetry analysis and its application to the hidden order in URuSi

Ishitobi, Takayuki

The recently introduced cluster multipole theory offers a novel perspective on antiferromagnetically (AFM) ordered phases, illuminating their macroscopic symmetry. In this presentation, we apply the cluster multipole theory for clarifying local symmetry at atomic sites without the need for technical advancements. By simply choosing the cluster center at atomic sites, one can easily identify local symmetry. We showcase the utility of this method applying to the hidden ordered phase of URuSi as a typical example. By assuming the ordering of atomic degrees of freedom with the ordering vector at q = (0,0,1), we successfully derive a complete local symmetry table. This framework allows for the potential identification of the order parameter, which can be achieved through NMR or RXS experiments, particularly under uniaxial strain and/or magnetic fields.