Localized Triplons and Site Stuffing in the Quantum Dimer Magnet BiYbGeO${}_5$

Abstract

Thermodynamic and muon spin-relaxation measurements have recently highlighted BiYbGeO${}_5$ as a new example of a rare-earth-based quantum dimer magnet with isolated Yb${}^{3+}$ spin-$\frac{1}{2}$ dimers. However, direct spectroscopic evidence of the triplet excitations and measurements of the structural disorder are lacking. In this work, polycrystalline BiYbGeO${}_5$ 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 Yb${}^{3+}$ sites are replaced by non-magnetic Bi${}^{3+}$, introducing significant structural disorder. Inelastic neutron scattering shows dispersionless triplon excitations, consistent with localized, non-interacting spin dimers. Fits to the triplet excitation spectrum identify an XXZ-type anisotropic exchange with $J_{XX}$ = 0.11(2) meV and $J_Z=0.15(1)$ meV. These findings establish BiYbGeO${}_5$ 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.

6 pages, 5 figures

References in corpus (8)

• Mantid - Data Analysis and Visualization Package for Neutron Scattering and $\mu SR$ Experiments
• Lightly stuffed pyrochlore structure of single-crystalline Yb2Ti2O7 grown by the optical floating zone technique
• Neutron Spectroscopic Study of Crystalline Electric Field Excitations in Stochiometric and Lightly Stuffed Yb2Ti2O7
• Novel Strongly Spin-Orbit Coupled Quantum Dimer Magnet: Yb${}_2$Si${}_2$O${}_7$
• Experimental observation of magnetic dimers in diluted Yb:YAlO${}_3$
• Effects of "stuffing" on the atomic and electronic structure of the pyrochlore Yb${}_2$Ti${}_2$O${}_7$
• Two-qubit Quantum Logic Gate in Molecular Magnets
• High-fidelity dimer excitations using quantum hardware