Effective Hamiltonian for charge-ordered Yb4As3

Yb4As3 is a 4f compound showing a heavy-fermion-like behavior in spite of i ts low carrier concentration. Previous studies have shown that Yb3+ chains are formed along [111] below the charge ordering temperature T-c = 290 K. I n this paper an effective Hamiltonian to describe the low-energy physics of the Yb3+ chain is derived by properly taking into account its unique struc ture. The resulting Hamiltonian is surprisingly simple, showing a hidden sy mmetry previously unnoticed. In addition it gives a support to a recent wor k by Oshikawa et al.. which emphasizes the importance of the Dzyaloshinsky- Moriya term. It is also pointed out that the structure of the Yb3+ chain le ads to a mixing between the almost localized 4f state and the 5d electron-l ike carriers.