Rational synthesis of a new Haldane chain compound by predicted pressure-induced phase modification

The realization and discovery of novel topological quantum states is a fascinating intersection field of solid-state chemistry, materials science, and condensed matter physics. As a typical model of symmetry-protected topological states, the Haldane phase oxides are still rare to date. Here, we report the precise synthesis of a new predicted Haldane chain compound, the high-pressure (HP) BaNi 2 V 2 O 8 polymorph, by pressure-induced phase modification. The collective experimental characterizations and theoretical calculations emphasize the nonmagnetic ground state of the Haldane phase with a field-induced quantum magnetic transition at a critical field of 16.8 T at 1.6 K. Notably, Mg-doped BaNi 2 V 2 O 8 exhibits a spin-glass-like state, which is in sharp contrast to the antiferromagnetic ordering observed in the Mg-doped A Ni 2 V 2 O 8 ( A  = Pb and Sr). Further spin Hamiltonian calculations and experimental investigations on the prototypical family of A Ni 2 V 2 O 8 ( A  = Ba and Sr) and derivatives unveil that the variation of the inter- and intra-chain magnetic couplings induced by the symmetry change may be crucial in determining the ground state of the Haldane phase destabilized by the substitution ions. The discoveries of this new HP-BaNi 2 V 2 O 8 Haldane phase provide a local-structure-based new platform to intensify the understanding of quantum phase transition in the Haldane system.