Fig. 3: Selective boundary non-Hermitian skin effect (NHSE) and non-monotonic state dynamics.
From: Activating non-Hermitian skin modes by parity-time symmetry breaking
a Hg,2D hosts bulk states with unbroken parity-time (\({{{{{{{\mathcal{PT}}}}}}}}\)) symmetry (black) and \({{{{{{{\mathcal{PT}}}}}}}}\)-broken topological edge states under open/periodic boundary conditions (OBCs/PBCs) along x/y direction (gray). Under full OBCs, the latter experiences y-NHSE and become corner-localized (red). b \({H}_{g,2{{{{{{{\rm{D}}}}}}}}}^{{\prime} }\) is deformed from Hg,2D such that \({{{{{{{\mathcal{PT}}}}}}}}\) symmetry is restored for the branch of edge states (green) with Im(E) > 0, which remains edge-localized; and broken for the bulk states (black), which are thus edge-localized due to y-NHSE. c, d depict the dynamical evolution of a center-localized initial state (black dot) due to Hg,2D and \({H}_{g,2{{{{{{{\rm{D}}}}}}}}}^{{\prime} }\) respectively, with the size of blue dots indicating evolved state density. Qualitatively distinct stages occur before and after encountering the upper boundary; in d, the upper edge state evolves into the left edge state, leading to non-monotonic 〈y〉. Parameters are u = 0.2, g = 0.3, t1 = 0.3 and \({t}_{2}^{{\prime} }=0.1\), with system size Nx = Ny = 20.
