Phonon Hall viscosity from phonon-spinon interactions

TL;DR

This paper investigates how proximity to a quantum phase transition in cuprate parent compounds induces a significant phonon Hall viscosity through spinon-phonon interactions, revealing nonanalytic behavior at zero temperature.

Contribution

It introduces a model for spinon-phonon coupling and demonstrates the emergence of divergent phonon Hall viscosity near a quantum critical point.

Findings

Nonanalytic Hall viscosity across the transition

Divergent second derivative at zero temperature

Chiral phonons induced by spinon interactions

Abstract

Motivated by experimental observations, Samajdar et al. [Nature Physics 15, 1290 (2019)] have proposed that the insulating Neel state in the parent compounds of the cuprates is proximate to a quantum phase transition to a state in which Neel order coexists with semion topological order. We study the manner in which proximity to this transition can make the phonons chiral, by inducing a significant phonon Hall viscosity. We describe the spinon-phonon coupling in a lattice spinon model coupled to a strain field, and also using a general continuum theory constrained only by symmetry. We find a nonanalytic Hall viscosity across the transition, with a divergent second derivative at zero temperature.