Doniach phase diagram for the Kondo lattice model on square and triangular lattices

Abstract

In this study we systematically investigate the interplay between Ruderman-Kittel-Kasuya-Yosida (RKKY) and Kondo couplings in the Doniach phase diagram on square and triangular lattices using advanced many-body techniques. Our findings indicate that the simple Doniach phase diagram is inadequate to fully capture the complexity of the competition even on these simple lattices. First, we discovered that the potential energy arising from geometric frustration is comparable to that of RKKY coupling, effectively suppressing long-range antiferromagnetic (AFM) order on the half-filled triangular lattice. Second, while long-range AFM order can be successfully established on the square lattice, Kondo singlets begin to form within the long-range magnetic phase. Upon doping with holes, geometric frustration on the triangular lattice is partially relieved, giving rise to two distinct magnetic orders that emerge unexpectedly. These orders are intimately linked to the topology of the interacting Fermi surface. Our comprehensive analysis of the Kondo lattice model on both lattices reveals a significant interplay between geometric frustration as well as RKKY and Kondo couplings in low-dimensional systems and offers valuable insights into the discovery of novel phases in related materials.