High Impact Physics

A seemingly still crystal is alive with synchronized atomic motions. Now, angular momentum has been observed flowing coherently between distinct lattice vibrational modes, revealing a hidden propagation of rotational features inside the crystal.

Non-Hermitian systems support non-trivial topological effects, yet eigenvalue braiding remains difficult to control and observe. Now, active tuning of laser modes enables programmable and directly observable braiding on an integrated photonic chip.

How angular momentum is exchanged and conserved among lattice modes has been difficult to measure experimentally, but has now been observed via a coherent three-phonon scattering process in a topological insulator.

That author's affiliation: UNSW Sydney First author institution: UNSW Sydney Last author institution: University of Canberra

A tunable artificial crystal in a shallow GaAs quantum well is shown to enable interaction-driven insulating behaviour. Electrostatic control tunes the band structure from graphene-like to kagome-like bands.