Magnon hydrodynamics in an atomically thin ferromagnet
Summary
Strong interactions between particles can lead to emergent collective excitations. Spin waves, known as magnons, have been predicted to reach a strongly interacting hydrodynamic regime, where they form a slow collective density mode. In this work, we isolate exfoliated sheets of chromium trichloride (CrCl3), where magnon interactions are strong, and develop a technique to measure the collective magnon dynamics though nearby nitrogen-vacancy centers in diamond. Thermal magnetic fluctuations
Content
# Magnon hydrodynamics in an atomically thin ferromagnet
*Published: 2026 May 21*
Strong interactions between particles can lead to emergent collective
excitations. Spin waves, known as magnons, have been predicted to reach a
strongly interacting hydrodynamic regime, where they form a slow collective
density mode. In this work, we isolate exfoliated sheets of chromium trichloride
(CrCl3), where magnon interactions are strong, and develop a technique to
measure the collective magnon dynamics though nearby nitrogen-vacancy centers in
diamond. Thermal magnetic fluctuations generated by monolayer CrCl3 increase
upon decreasing temperature; this anomalous trend may be a consequence of the
damping rate of a low-energy magnon sound mode that sharpens as magnon
interactions increase with increasing temperature. By measuring the magnetic
fluctuations emitted by thin multilayer CrCl3 in the presence of a
variable-frequency drive field, we obtain spectroscopic evidence for this
two-dimensional magnon sound mode.
DOI: 10.1126/science.adp2397