Instability to partial Kondo-singlet state in the Kondo necklace model on frustrated lattices

Abstract

We present our theoretical results on the Kondo necklace model, which is known to give a good description of the half-filled state of the Kondo lattice model, on geometrically frustrated lattices. We employ the Lanczos exact diagonalization method as well as the bond-operator mean-field approximation to clarify the magnetic state at zero temperature. We examine a possibility of relieving severe frustration by making a spatially-periodic arrangement of magnetic ordered sites and nonmagnetic ones, i.e., the magnetic moments vanish periodically due to the Kondo singlet formation. We call the composite of magnetic and Kondo-singlet subsystems ‘partial Kondo-singlet state’, by analogy with the partial order in frustrated spin systems. We demonstrate that small clusters of 1D and 2D frustrated models show a tendency to exhibit the partial Kondo-singlet formation, and compare the results with those by the bond-operator mean-field approximation.