Unidirectional reflectionless anti-parity-time-symmetric photonic lattices of thermal atoms

Abstract

We experimentally demonstrate an anti-parity-time (anti-$PT$)-symmetric photonic lattice in thermal cesium atoms driven by two standing-wave laser fields. Such a lattice possesses anti-$PT$-symmetric susceptibility, of which the real (imaginary) part is an odd (even) function of position. By manipulating the intensities and phases of the two standing-wave fields, we experimentally observe unidirectional reflectionless propagation at the exceptional points. Our work provides a platform to study the scattering property of anti-$PT$-symmetric systems.