Encoding Complexity within Supramolecular Analogues of Frustrated   Magnets
  At the heart of systems chemistry lies the idea that supramolecular interactions can give rise to complex and unexpected collective states that emerge on a fundamentally different lengthscale to that of the interactions themselves. While in certain cases - e.g. the self-assembly of virus-like polyhedral cages from coordination building blocks - it is possible to control emergence in a systematic manner, the development of general approaches remains a fundamental challenge in the field. In the conceptually-related domain of frustrated magnetism - where collective states give rise to exotic physics of relevance to data storage and spintronics - the task of predicting emergent behaviour is simplified through control over the geometry and form of the magnetic interactions from which complexity arises. Seeking to combine approaches from these two fields, we study here the solid phases of inorganic polymer chains assembled from non-magnetic gold(I)/silver(I) cations and cyanide anions. We show the periodic inter-chain potential encodes a supramolecular interaction that can be tuned to mimic different magnetic interactions between XY spins ("spin rotors"). Because the chains pack on a triangular lattice, the crystal structures of gold(I)/silver(I) cyanides can be interpreted in terms of the phase behaviour of triangular XY magnets. Complex magnetic states predicted for this family - including hidden quadrupolar order and emergent spin-vortex quasiparticles - are realised for the first time in the structural chemistry of these cyanide polymers. In this way we demonstrate both how simple inorganic materials might behave as structural analogues of otherwise-unrealisable "toy" spin models, and also how a theoretical understanding of those models might be used to predict and control emergent phenomena in chemical systems. 
Andrew B. Cairns, Matthew J. Cliffe, Joseph A. M. Paddison, Dominik   Daisenberger, Matthew G. Tucker, Fran\c{c}ois-Xavier C...
cond-mat.mtrl-sci