Research: Magnon Landau levels in strained antiferromag­nets

Strain has become an important tool to engineer novel states of matter. In particular, inhomogeneous strain applied to lattice systems can induce artificial gauge fields for particles moving on this lattice. Here we demonstrate how to engineer a novel state in Mott-insulating magnets, namely an antiferromagnet with a Landau-level excitation spectrum of magnons. We consider a honeycomb-lattice Heisenberg model and show that triaxial strain leads to equally spaced pseudo-Landau levels at the upper end of the magnon spectrum, with degeneracies characteristic of emergent supersymmetry. We also present a particular strain protocol which induces perfectly quantized magnon Landau levels over the whole bandwidth. We discuss experimental realizations and generalizations.

M. M. Nayga, S. Rachel, M. Vojta,
Magnon Landau levels and emergent supersymmetry in strained antiferromagnets,
Phys. Rev. Lett. 123, 207204 (2019), arXiv:1903.05097