Large phonon thermal Hall conductivity in the antiferromagnetic insulator Cu3TeO6

Significance Phonons are believed not to be able to generate a thermal Hall signal due to their lack of charge or spin. However, since the first discovery of a phonon thermal Hall effect in the paramagnetic insulator Tb3Ga5O12, much larger signals have been observed in several other families of insulators, which raises a fundamental question: How can phonons become chiral in a magnetic field? Most of the insulators that exhibit a phonon Hall effect have some special feature, believed to be a key to the underlying mechanism. Here, our discovery of a large phonon thermal Hall conductivity in a simple material with none of the special features of the previous cases opens up the subject into a much broader question.