Physics (Internal)

Many-body quantum entanglement: frustration and spin-orbit coupling in magnetic solids

This event is part of the Biophysics/Condensed Matter Seminar Series.

Quantum entanglement, a key feature of two-body quantum mechanics, can produce counter intuitive phenomena such as fractional charge when a many-body system develops collective entanglement. However, macroscopic systems often develop classical symmetry-breaking order instead. What mechanisms can support entanglement in 3D solids?

Spin-orbit coupling, a relativistic effect which links the electron spin to the crystalline lattice, suggests an approach. I will use it to discuss models for a recently-discovered family of iridate materials whose spin-orbit moments form honeycomb-like 3D lattices. Their unusual magnetism is shown to arise from a frustrated spin-lattice-coupled interaction. An infinite-dimensional approximation yields numerical access to a rich phase diagram, including a nearby 3D quantum spin liquid phase. The bosonic spins in this phase are collectively entangled, producing emergent flux-loops and fermions. Remarkably, they remain deconfined up to a finite-temperature transition. These features indicate new avenues for experimentally producing and identifying collective entanglement in solids.