Theoretical Model for the Semimetal Yb_4As_3

TL;DR

This paper develops a theoretical model explaining the unusual properties of Yb_4As_3, including its phase transition, charge ordering, low carrier density, heavy-fermion behavior, and low-temperature energy scales.

Contribution

It introduces a band Jahn-Teller effect-based model that accounts for multiple complex phenomena in Yb_4As_3, providing a comprehensive theoretical framework.

Findings

Charge ordering of Yb ions at 300 K

Heavy-fermion behavior around 50 K

Low-energy scale near 0.2 K due to low-density carriers

Abstract

We present a model which can explain semiquantitatively a number of the unusual properties of \mbox{Yb$_4$As$_3$}. The structural phase transition at $T_{\text{c}}\simeq300\,\mbox{K}$ is described by a band Jahn-Teller effect of correlated electrons and is interpreted as a charge ordering of the Yb ions. The low carrier concentration in the low-temperature phase follows from the strong electron correlations of the 4f-holes on the Yb sites and can be viewed as self-doping of charge-ordered chains. The observed heavy-fermion behaviour is on a scale of $T^\ast\simeq50\,\mbox{K}$ and is due to spinon-like excitations in the Yb$^{3+}$-chains. The appearance of a second low-energy scale around 0.2\,K is due to the Fermi energy of the low-density carriers.