Microscopic Theory of Multipole Ordering in f-Electron Systems

Abstract EN

A microscopic framework to determine multipole ordering in f-electron systems is provided on the basis of the standard quantum field theory.

For the construction of the framework, a seven-orbital Hubbard Hamiltonian with strong spin-orbit coupling is adopted as a prototype model.

A type of multipole and ordering vector is determined from the divergence of multipole susceptibility, which is evaluated in a random phase approximation.

As an example of the application of the present framework, a multipole phase diagram on a three-dimensional simple cubic lattice is discussed for the case of n=2, where n denotes the average f-electron number per site.

Finally, future problems concerning multipole ordering and fluctuations are briefly discussed.