From mixed valence to pseudo-one-dimensional spin chains in Yb 4As 3

Abstract

According to a recently developed model, the Yb 3+-ions in the heavy-fermion system Yb 4As 3 are positioned on parallel, quasi-one-dimensional chains at low temperatures. A small interchain coupling J′ leads to a strong magnetic-field dependence of the linear specific-heat coefficient γ. Within linear spin-wave approximation, it is shown that the six spin-wave excitation branches ω κ( q,H) determine the low-temperature thermodynamics of Yb 4As 3. Most importantly, field-induced gaps scaling as Δ ⋍ √JJ′ appear at q = γ,A . For J′ = 10 −4 J, a good agreement with the experimental variation of γ( H) achieved.