No Sign of Staggered Magnetization in the Recently Discovered Quantum Dimer Magnet - Yb₂Si₂O₇

In 2019, Hester et al. reported Yb₂Si₂O₇ as the first rare-earth-based Quantum Dimer Magnet (QDM), with low temperature physics that can be traced back to a topic found in any quantum mechanics textbook: the interaction of two spin 1/2 particles subjected to a magnetic field.  Many versions of the QDM have been studied with 3d transition metal species, showing a "Bose-Einstein Condensation (BEC) dome" in the magnetic field vs. temperature phase diagram, where within the dome an antiferromagnetic order is established.  Unlike these traditional QDM's the BEC dome for Yb₂Si₂O₇ appears to contain two separate phases, however, previous experimental work has not directly observed the antiferromagnetic order in any region of the dome.  Here we present elastic neutron scattering data as a function of magnetic field strength throughout the dome.  This suggests either an issue with thermal equilibration, or that the size of the ordered moment within the dome is small due to quantum fluctuations.  For the latter to be the case, additional anisotropic terms in the Hamiltonian are required.