Photonic corner skin modes

Useful in the enhancement of light-matter interaction, localization of light is at the heart of photonics studies. Different approaches have been proposed to localize light, including those based on dynamical localization, topological trivial or nontrivial defects in the band gap of photonic crystals, and bound states in the continuum. Recent studies on non-Hermitian skin effect have provided us new means to localize waves. In this work, we propose a new method towards localized light, called photonic corner skin modes arising from second-order non-Hermitian skin effect and gain-loss symmetry on a lattice. Specifically, we propose to make use of small pseudo-inversion symmetric gain/loss, which does not close the band gap, to realize a photonic Chern insulator with chiral edge states. The chiral edge states then accumulate at certain corners of the system. Intriguing phenomena such as corner skin modes arising from an underlying bipolar second-order non-Hermitian skin effect and multiple-corner skin modes are predicted in continuous systems.