Mixed Hydroxide Flux and Field-Tailoring Technology for Novel Quantum Materials Synthesis

One of the primary challenges in the rational synthesis of materials is thermodynamics, which either facilitates the formation of trivial phases or induces undesired inherent distortions that adversely alter physical properties. In this talk, we demonstrate how innovative techniques can overcome these obstacles to control ground states or even induce emergent phenomena in novel quantum materials.

We first delve into a recently developed mixed-flux method [1-3] to overcome thermodynamic barriers and stabilize kinetic phases. With this technique, we synthesized a new layered material of K_xNi₄S₂, whose ground state changes from a Dirac-metal to a flat-band induced magnetic metal, depending on K-content. In addition, by incorporating a monolayer of Ni-Pb sheet, we synthesized a novel layered compound, KPbNi₅S₂. Furthermore, KPbNi₅S₂ can be stacked with KNi₂S₂ to create another heterolayered [KPbNi₅S₂][KNi₂S₂].

Next, we show how inherent lattice distortions can be mitigated by a newly developed field-tailoring technology that applies magnetic field during crystal growth [4]. This development addresses a major challenge of our research community: numerous theoretical works predicting exotic states for spin-orbit-coupled, strongly correlated materials have rarely been experimentally confirmed. These discrepancies are due chiefly to the extreme sensitivity to inherently structural distortions. Using 5d iridates as examples, we demonstrate that “field-altered” materials not only are much less distorted but also exhibit phenomena absent in their “non-altered” counterparts.

In conclusion, we demonstrate two new versatile synthesis techniques that pave the way for quantum materials by design. These methods open new avenues for discovering novel quantum states and materials otherwise unavailable.