Gigahertz topological valley Hall effect in NEMS phononic crystals
sciencedaily.com
sciencedaily.com
> Topological phononic crystals can manipulate elastic waves that propagate in solids without being backscattered, and could be used to develop integrated acousto-electronic systems for classical and quantum information processing. However, acoustic topological metamaterials have been mainly limited to macroscale systems that operate at low (kilohertz to megahertz) frequencies. Here we report a topological valley Hall effect in nanoelectromechanical aluminium nitride membranes at gigahertz (up to 1.06 GHz) frequencies. We visualize the propagation of elastic waves through phononic crystals with high sensitivity (10–100 fm) and spatial resolution (10–100 nm) using transmission-mode microwave impedance microscopy. The valley Hall edge states, which are protected by band topology, are observed in both real and momentum space. Robust valley-polarized transport is evident from wave transmission across local disorder and around sharp corners. We also show that the system can be used to create an acoustic beamsplitter.
> The quantum Hall effect, in addition to being observed in two-dimensional electron systems, can be observed in photons. Photons do not possess inherent electric charge, but through the manipulation of discrete optical resonators and coupling phases or on-site phases, an artificial magnetic field can be created. [17][18][19][20][21] This process can be expressed through a metaphor of photons bouncing between multiple mirrors. By shooting the light across multiple mirrors, the photons are routed and gain additional phase proportional to their angular momentum. This creates an effect like they are in a magnetic field.
The Hall effect article describes how Superposition states can be prepared with the Hall effect.
So, in crystal lattices, is there less noise due to scattering?