Glide symmetry breaking and Ising criticality in the quasi-1D magnet CoNb$_2$O$_6$

Understand

We construct a microscopic spin-exchange Hamiltonian for the quasi-1D Ising magnet CoNb$_2$O$_6$ that captures detailed and hitherto-unexplained aspects of its dynamic spin structure factor.

• We perform a symmetry analysis that recalls that an individual Ising chain in this material is buckled, with two sites in each unit cell related by a glide symmetry.
• Combining this with numerical simulations benchmarked against neutron scattering experiments, we argue that the single-chain Hamiltonian contains a staggered spin-exchange term.
• We further argue that the transverse-field-tuned quantum critical point in CoNb$_2$O$_6$ corresponds to breaking this glide symmetry, rather than an on-site Ising symmetry as previously believed.