Effective Hamiltonian for Charge-Ordered Yb4As3

Yb 4 As 3 is a 4 f compound showing a heavy-fermion-like behavior in spite of its low carrier concentration. Previous studies have shown that Yb 3+ chains are formed along <111> below the charge ordering temperature T c =290 K. In this paper an effective Hamiltonian to describe the low-energy physics of the Yb 3+ chain is derived by properly taking into account its unique structure. The resulting Hamiltonian is surprisingly simple, showing a hidden symmetry previously unnoticed. In addition it gives a support to a recent work by Oshikawa et al. , which emphasizes the importance of the Dzyaloshinsky-Moriya term. It is also pointed out that the structure of the Yb 3+ chain leads to a mixing between the almost localized 4 f state and the 5 d electron-like carriers.