Order from Disorder in the Two-Dimensional Kondo-Necklace

Abstract

We analyze the effects of site-dilution disorder on the thermodynamic properties of the two-dimensional Kondo necklace using finite-temperature stochastic series expansion. Results will be discussed for the dependence on dilution concentration, temperature, and Kondo exchange-coupling strength of the uniform susceptibility, the staggered structure factor, and the Chakravarty-Halperin-Nelson ratio. Dilution is shown to induce effective free-spin clusters in the gapped phase of the clean system with a low-temperature Curie constant renormalized below 1/4. Furthermore, dilution is demonstrated to generate antiferromagnetic order in the quantum disordered phase of the clean system, i.e. order-from-disorder. In turn, the quantum critical point of the clean system, separating an antiferromagnetic from a paramagnetic dimerized state at a critical Kondo exchange-coupling strength $J_{c}\approx1.4$ is suppressed. Finally, speculations on a renormalized classical behavior in the dilution induced ordered phase are stated.