Abstract
Thermodynamic and muon spin relaxation measurements have recently highlighted BiYbGeO5 as a new example of a rare-earth-based quantum dimer magnet with isolated Yb3+ spin-1/2 dimers. However, direct spectroscopic evidence of the triplet excitations and measurements of the structural disorder are lacking. In this work, polycrystalline BiYbGeO5 was synthesized using conventional high-temperature solid-state methods and investigated via high-resolution neutron powder diffraction and inelastic neutron scattering. Diffraction measurements down to 58 mK reveal no signatures of magnetic order and indicate that nearly 20% of Yb3+ sites are replaced by nonmagnetic Bi3+, introducing significant structural disorder. Inelastic neutron scattering shows dispersionless triplon excitations, consistent with localized, noninteracting spin dimers. Fits to the triplet excitation spectrum with an XXZ-type anisotropic exchange give JXX = 0.100(1) meV and JZ = 0.202(1) meV. These findings establish BiYbGeO5 as a structurally disordered but magnetically well-isolated quantum dimer system, providing a model platform for studying the resilience of entangled spin states to site dilution.
| Original language | English |
|---|---|
| Article number | 224410 |
| Pages (from-to) | 1-7 |
| Number of pages | 7 |
| Journal | Physical Review B |
| Volume | 112 |
| Issue number | 22 |
| DOIs | |
| State | Published - Dec 5 2025 |
Funding
R.K. and G.H. would like to thank R. Ganesh for insightful conversations related to this work. We would also like to thank C. Sarkis for facilitating the measurements using HYSPEC for this work. We also extend our gratitude to Carter Fortuna for synthesizing many variants of this material. A portion of this work used resources at the High-Flux Isotope Reactor and the Spallation Neutron Source, which are DOE Office of Science User Facilities operated by Oak Ridge National Laboratory. The beamtime was allocated to POWDER (HB-2A) and HYSPEC (BL-14B) on Proposals No. IPTS-32979 and No. IPTS-35019, respectively.