Alpha-RuCl3 is a Kitaev honeycomb magnet — a material whose magnetic interactions are geometrically frustrated in the specific way needed to host a quantum spin liquid, a phase of matter where spins are entangled but never freeze into a fixed pattern. In theory, this phase supports exotic excitations useful for quantum computing. In practice, alpha-RuCl3 orders magnetically at low temperatures, and the spin liquid is inaccessible.
Cônsoli, Day-Roberts, Knolle, Botana, and Erten (2026) show that stacking alpha-RuCl3 on top of MnPS3 — a van der Waals antiferromagnet — provides a staggered magnetic field that drives the combined system into phases that neither material can reach alone. The proximity effect from the antiferromagnet acts as an external knob that pushes the Kitaev magnet through its phase diagram without changing its chemistry. The resulting phases include an antichiral Kitaev spin liquid, a nonmagnetic nematic phase, and several types of skyrmion crystals. None of these exist in bulk alpha-RuCl3. None exist in bulk MnPS3. They exist only in the interface between them.
The method is subtraction by addition. Adding a neighbor with the right symmetry subtracts the magnetic ordering that blocked the spin liquid. The staggered field from MnPS3 does not simply apply a magnetic field — it applies a field that alternates sign on each sublattice, which selectively suppresses the unwanted ordering while leaving the desired frustration intact. The surgery is precise because the tool (staggered field) has the same spatial symmetry as the obstruction (zigzag magnetic order).
The general principle: a phase of matter can be inaccessible in any single material but accessible at the boundary between two materials. The interface provides degrees of freedom — specifically, symmetry-matched fields from the neighbor — that no bulk perturbation can replicate. The phase space of a heterostructure is larger than the union of its components' individual phase spaces.