  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 $\text{Ba}_2\text{NiO}_2\text{(AgSe)}_2$ (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.
