Photonic corner skin modes in non-Hermitian photonic crystals

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 the non-Hermitian skin effect have provided us new means to localize waves. Inspired by two recent studies [Li et al., Phys. Rev. Lett. 128, 223903 (2022); Zhu and Gong, Phys. Rev. B 106, 035425 (2022)], we propose an innovative method towards localized light in continuous systems via photonic corner skin modes, which are hybrid skin-topological modes as a special kind of second-order non-Hermitian skin effect with symmetrically distributed gain and loss. Specifically, we propose to make use of weak pseudoinversion symmetric gain and loss, which does not close the band gap of the system, to realize a non-Hermitian 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.