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arXiv · 2606.26243

Bobkingite, a new coupled sawtooth chain platform

P. Peter Stavropoulos·Aleksandar Razpopov·Harrison LaBollita·Michael R. Norman·Antia S. Botana·Roser Valentí
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Abstract

We investigate the mineral bobkingite, \ce{Cu5(OH)8Cl2(H2O)2}, as a potential realization of the sawtooth chain. Using \textit{ab initio} methods, we estimate the magnetic exchange couplings and find that bobkingite hosts quasi-one-dimensional sawtooth chains, with residual three-dimensional interactions strongly suppressed by the crystal geometry. Examining the full exchange network, we find that the classical model exhibits an extensive manifold of nearly degenerate states with emergent two-dimensional character, which spin-wave theory shows to persist to leading order in quantum fluctuations as Ising degrees of freedom. Unlike other sawtooth candidates, bobkingite has negligible vertical interchain coupling, preserving a one-dimensional degeneracy even in the presence of ordering, suggesting that any long-range order is weak. Thermal fluctuations may thus stabilize a finite-temperature classical spin liquid regime, with a cascade of transitions upon cooling into successively lower-dimensional degenerate states, making bobkingite a compelling platform for exploring sawtooth chain physics.

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P. Peter Stavropoulos, Aleksandar Razpopov, Harrison LaBollita, Michael R. Norman, Antia S. Botana, Roser Valentí. 2026-06-24. Bobkingite, a new coupled sawtooth chain platform. https://arxiv.org/abs/2606.26243

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