Speaker
Description
In the search for exotic entangled states in quantum magnets, understanding how disorder affects the stability and properties of quantum ground states remains an open problem. Quantum dimer magnets, where neighboring spins form entangled singlet pairs, provide a particularly clean platform for addressing this question.
Our study centers on the rare-earth dimer magnet BiYbGeO₅, previously identified by Mohanty et al. using heat capacity, magnetometry, and muon-spin relaxation as only the second known rare-earth–based quantum dimer system. BiYbGeO₅ consists of quasi-two-dimensional layers of magnetic, effective spin-1/2 Yb³⁺ ions that form entangled dimers.
Using neutron diffraction, we uncover an unexpectedly large degree of intrinsic disorder: approximately 20% of the magnetic Yb sites are occupied by non-magnetic Bi ions. Remarkably, despite this large level of disorder, our inelastic neutron scattering measurements reveal sharp, well-defined triplet excitations characteristic of a dimerized ground state. These excitations are remarkably robust, persisting to temperatures well above 10 K and occurring at energies (~0.15 meV) consistent with those predicted by Mohanty et al.
I will present these results on BiYbGeO₅, along with initial measurements on the related compounds BiErGeO₅ and BiDyGeO₅, which display starkly different disorder trends. Together, our findings demonstrate that quantum dimer ground states can remain intact even in the presence of substantial structural randomness. More broadly, they challenge the prevailing assumption that strong disorder necessarily destroys fragile, entangled phases. Combined with the natural glass-forming tendency of the Bi–Ge–O system, this work opens the door to exploring a largely unexplored regime: the survival of quantum entanglement in an amorphous solid.
| Keyword-1 | Quantum entanglement |
|---|---|
| Keyword-2 | Neutron scattering |
| Keyword-3 | Magnetic disorder |