Ferroelectricity-Driven Phonon Berry Curvature and Nonlinear Phonon Hall Transports.

Berry curvature (BC) governs topological phases of matter and generates anomalous transport. When a magnetic field is applied, phonons can acquire BC indirectly through spin-lattice coupling, leading to a linear phonon Hall effect. Here, we show that polar lattice distortion directly couples to a phonon BC dipole, which causes a switchable nonlinear phonon Hall effect. In a SnS monolayer, the in-plane ferroelectricity induces a phonon BC and leads to the phononic version of the nonvolatile BC memory effect. As a new type of ferroelectricity-phonon coupling, the phonon Rashba effect emerges and opens a mass gap in tilted Weyl phonon modes, resulting in a large phonon BC dipole. Furthermore, our ab initio non-equilibrium molecular dynamics simulations reveal that nonlinear phonon Hall transport occurs in a controllable manner via ferroelectric switching. The ferroelectricity-driven phonon BC and corresponding nonlinear phonon transports provide a novel scheme for constructing topological phononic transport/memory devices.