Effective Hamiltonian for Charge-Ordered Yb₄As₃

Abstract

Yb₄As₃ is a 4f compound showing a heavy-fermion-like behavior in spite of its low carrier concentration. Previous studies have shown that Yb³⁺ 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 Yb³⁺ 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 Yb³⁺ chain leads to a mixing between the almost localized 4f state and the 5d electron-like carriers.