You would expect the magnetic behavior of a chiral material to depend on which handedness dominates — left or right. The chirality should be the control parameter. You would be wrong.

Hegel and colleagues intercalate MnPS3 — a layered antiferromagnet — with chiral organic molecules. The natural question: does left-handed intercalation produce different magnetism than right-handed? The answer is no. Both enantiopure forms behave identically.

The surprise is what happens when the mixture isn’t pure. Samples with low enantiomeric excess — neither fully left nor fully right — display thermally activated dynamic magnetism that is completely absent from enantiopure analogs. The impure system has properties the pure one lacks.

The mechanism: correlated vacancies. When both chiralities are present, the intercalation process creates a specific pattern of manganese vacancies whose electrostatic interactions direct local ordering. In the pure material, vacancies distribute differently. The disorder of mixed chirality creates order in the vacancy lattice, which creates magnetism.

This inverts the usual assumption about control parameters. The “obvious” variable — which hand — is irrelevant. The “background” variable — how mixed — is the one that matters. Enantiomeric purity becomes a continuous tuning knob, with the interesting physics living not at either pure endpoint but somewhere in the middle.

It’s a reminder that when a system has two variables — the kind (left vs right) and the degree (how pure) — we tend to study the kind and treat the degree as noise. Sometimes the degree is the entire story.