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Durham University

Department of Physics

Staff profile

Publication details for Professor Tom Lancaster

Liu, J., Kittaka, S., Johnson, R. D., Lancaster, T., Singleton, J., Sakakibara, T., Kohama, Y., van Tol, J., Ardavan, A., Williams, B. H., Blundell, S. J., Manson, Z. E., Manson, J. L. & Goddard, P. A. (2019). Unconventional Field-Induced Spin Gap in an S=1/2 Chiral Staggered Chain. Physical Review Letters 122(5): 057207.

Author(s) from Durham


We investigate the low-temperature magnetic properties of the molecule-based chiral spin chain
½CuðpymÞðH2OÞ4SiF6 · H2O (pym ¼ pyrimidine). Electron-spin resonance, magnetometry and heat
capacity measurements reveal the presence of staggered g tensors, a rich low-temperature excitation
spectrum, a staggered susceptibility, and a spin gap that opens on the application of a magnetic field. These
phenomena are reminiscent of those previously observed in nonchiral staggered chains, which are
explicable within the sine-Gordon quantum-field theory. In the present case, however, although the sineGordon model accounts well for the form of the temperature dependence of the heat capacity, the size of the
gap and its measured linear field dependence do not fit with the sine-Gordon theory as it stands. We propose
that the differences arise due to additional terms in the Hamiltonian resulting from the chiral structure of
½CuðpymÞðH2OÞ4SiF6 · H2O, particularly a uniform Dzyaloshinskii-Moriya coupling and a fourfold
periodic staggered field.