Enhanced Thermal Hall Effect in the Square-Lattice Néel State

October 7, 2019

Thermal Hall effect in the cuprate superconductors (Samajdar, et al.*)

Common wisdom about conventional antiferromagnets is that their low-energy physics is governed by spin–wave excitations. However, new experiments on several cuprate compounds have challenged this concept. An enhanced thermal Hall response in the pseudogap phase was identified, which, remarkably, persists even in the insulating parent compounds without doping. 

In a recent paper by Rhine Samajdar, Mathias Scheurer, Haoyu Guo and Prof. Subir Sachdev at Harvard, together with collaborators at UC Berkeley and UCSB, a possible explanation of the underlying physics is provided. To explain these surprising observations, the researchers study the quantum phase transition of a square-lattice antiferromagnet from a confining Néel state to a state with coexisting Néel and semion topological order, driven by an applied magnetic field. The proximity of the confining Néel state to the critical point can potentially explain the enhanced thermal Hall effect seen in experiments. 

* see R. Samajdar, M.S Scheurer, S. Chatterjee, H. Guo, C. Xu, and S. Sachdev, "Enhanced thermal Hall effect in the square-lattice Néel state,"  Nature Physics (2019) https://doi.org/10.1038/s41567-019-0669-3