Novel bipartite entanglement in the quantum dimer magnet Yb$_2$Be$_2$SiO$_7$

TL;DR

This study investigates the quantum dimer magnet Yb$_2$Be$_2$SiO$_7$, revealing that strong spin-orbit coupling induces novel entangled singlet states without magnetic order down to very low temperatures.

Contribution

It demonstrates that strong spin-orbit coupling in rare-earth quantum dimer systems can stabilize unique entangled ground states, expanding understanding of magnetic quantum materials.

Findings

Yb$^{3+}$ ions behave as effective spin-1/2 at low temperatures

No magnetic order observed down to 50 mK

Anisotropic exchange stabilizes a singlet ground state with specific wavefunction superpositions

Abstract

The quantum dimer magnet, with antiferromagnetic intradimer and interdimer Heisenberg exchange between spin-1/2 moments, is known to host an up/down - down/up singlet ground state when the intradimer exchange is dominant. Rare-earth-based quantum dimer systems with strong spin-orbit coupling offer the opportunity for tuning their magnetic properties by using magnetic anisotropy as a control knob. Here, we present bulk characterization and neutron scattering measurements of the quantum dimer magnet Yb$_2$Be$_2$SiO$_7$. We find that the Yb$^{3+}$ ions can be described by an effective spin-1/2 model at low temperatures and the system does not show signs of magnetic order down to 50 mK. The magnetization, heat capacity, and neutron spectroscopy data can be well-described by an isolated dimer model with highly anisotropic exchange that stabilizes a singlet ground state with a wavefunction up/up - down/down or up/up + down/down. Our results show that strong spin-orbit coupling can induce novel entangled states of matter in quantum dimer magnets.