Abstract
The competition between antiferromagnetic (AF) order and singlet formation is a central phenomenon of the Kondo and periodic Anderson Hamiltonians and of the heavy fermion materials they describe. In this paper, we explore the effects of an additional conduction band on magnetism in these models, and, specifically, on changes in the AF-singlet quantum critical point (QCP) and the one particle and spin spectral functions. To understand the magnetic phase transition qualitatively, we first carry out a self-consistent mean field theory (MFT). The basic conclusion is that, at half filling, the coupling to the additional band stabilizes the AF phase to larger hybridization in the PAM. We also explore the possibility of competing ferromagnetic phases when this conduction band is doped away from half filling. We next employ quantum Monte Carlo (QMC) which, in combination with finite size scaling, allows us to evaluate the position of the QCP using an exact treatment of the interactions. This approach confirms the stabilization of AF order, which occurs through an enhancement of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. QMC results for the spectral function and dynamic spin structure factor yield additional insight into the AF-singlet competition and the low temperature phases.
4 More- Received 7 February 2017
- Revised 8 May 2017
DOI:https://doi.org/10.1103/PhysRevB.95.235122
©2017 American Physical Society