Field-induced Bose-Einstein condensation and supersolid in the two-dimensional Kondo necklace

Abstract

The application of an external magnetic field of sufficient strength to a spin system composed of a localized singlet can overcome the energy gap and trigger bosonic condensation and so provide an alternative method to realize exotic phases of matter in real materials. Previous research has indicated that a spin Hamiltonian with on-site Kondo coupling may be the effective many-body Hamiltonian for Ba₂NiO₂(AgSe)₂ (BNOAS) and here we study such a Hamiltonian using a tensor network ansatz in two dimensions. Our results unveil a phase diagram which indicates the underlying phases of BNOAS. We propose, in response to the possible doping-induced superconductivity of BNOAS, a fermionic model for further investigation. We hope that our discovery can bring up further interest in both theoretical and experimental researches for related nickelate compounds.

Quantum magnets are a promising platform to aid in the search for a Bose-Einstein condensate and investigations into the underlying mechanisms of these materials are an active area of research. Here, the authors present a numerical study of the two-dimensional Kondo necklace model and consider the various phases which can occur under an applied magnetic field suggesting field-induced condensate phases may exist for the quantum magnet Ba₂NiO₂(AgSe)₂.