We report low-temperature specific-heat and thermal-expansion results on the carrier-poor system Yb4As3 as well as Yb4(As1-yXy)3, X: P, Sb. We infer that Yb4As3 behaves as a two-fluid system with almost decoupled spin and charge excitations. Quasi-one-dimensional spin excitations within S = 1/2 Heisenberg chains of Yb3+ ions formed in the charge-ordered state dominate the low-temperature thermodynamic properties. The effect of a magnetic field is to open a (pseudo-)gap in the low-energy spin-excitation spectrum. The Grüneisen parameter shows rather anomalous temperature and field dependences.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics