In one minute

Farokh Mivehvar, Helmut Ritsch and Francesco Piazza study a spinless ultracold Fermi gas trapped along an optical resonator and lit from the side by a laser near a cavity mode. Above a threshold pump intensity the gas breaks a Z2 symmetry into a periodic pattern that collectively scatters laser photons into the cavity. With blue detuning the emerging superradiant lattice has two possible dimerisations, and one of them gives topologically nontrivial bands with a nonzero Zak phase. When the Fermi momentum is near half the cavity wavenumber, a Peierls-like instability creates a topological insulator with a gap at the Fermi surface and a pair of edge states.

Superradiant Topological Peierls Insulator inside an Optical Cavity