Dynamical mean-field study of partial Kondo screening in the periodic Anderson model on the triangular lattice

TL;DR

This study uses dynamical mean-field theory to explore the interplay of Kondo screening and magnetic exchange in a frustrated triangular lattice, revealing a rich phase diagram with partial Kondo screening and magnetic order.

Contribution

It introduces a site-dependent DMFT approach to analyze the periodic Anderson model on a triangular lattice, uncovering novel partial Kondo screening phases.

Findings

At half-filling, the system is a non-magnetic Kondo insulator.

Partial Kondo screening occurs between magnetic and non-magnetic phases.

A crossover to ferromagnetic metallic states at low fillings.

Abstract

The competition between Kondo screening and indirect magnetic exchange is studied for a system with geometrical frustration using dynamical mean-field theory (DMFT). We systematically scan the weak- to strong-coupling regime of the periodic Anderson model on the triangular lattice for a wide range of fillings n. The magnetic phase diagram is derived using a site-dependent DMFT approach by self-consistent mapping onto three independent single-impurity models corresponding to the three correlated f orbitals in the unit cell. At half-filling, the system is a non-magnetic Kondo insulator for all considered interaction strengths U>0 which immediately develops into a non-magnetic metallic Kondo-singlet phase for fillings slightly below half-filling. On the other hand, indirect magnetic exchange between the f moments results in antiferromagnetic order at lower fillings. The antiferromagnetic and the Kondo-singlet phases are separated in the U-n phase diagram by an extended region of partial Kondo screening, i.e., a phase where the magnetic moment at one site in the unit cell is Kondo screened while the remaining two are coupled antiferromagnetically. At even lower fillings the system crosses over from a local-moment to a mixed-valence regime where the minimization of the kinetic energy in a strongly correlated system gives rise to a metallic and partially polarized ferromagnetic state.