arXiv subjects

Gan Liang

Publications and source records attributed to Gan Liang.

2 recordsLinked to original sources

arXiv2024

Topological and fractal defect states in non-Hermitian lattices

Higher dimensions provide fertile ground for diverse topological phases and their associated localization phenomena, thanks to the rich geometric features of boundaries and defects. In this paper, we investigate non-Hermitian lattices with defects and establish a correspondence between spectral winding topology, fractal structures, and defect-localized states in arbitrary dimensions. Through analytical derivation and numerical simulations, we demonstrate that defect states emerge only when the spectral winding number exceeds a threshold determined by the defect size, which is linked to their fractal characteristics. By utilizing the Green's function, we identify amplified responses at defects under external driving fields, strengthening the physical correspondence between these topological and fractal features. Our findings offer a universal framework for understanding defect-localized states in higher-dimensional non-Hermitian systems.

cond-mat.mes-hall↗

arXiv2024

Observation of scale-free localized states induced by non-Hermitian defects

Wave localization is a fundamental phenomenon that appears universally in both natural materials and artificial structures and plays a crucial role in understanding the various physical properties of a system. Usually, a localized state has an exponential profile with a localization length independent of the system size. Here, we experimentally demonstrate a new class of localized states called scale-free localized states, which has an unfixed localization length scaling linearly with the system size. Using circuit lattices, we observe that a non-Hermitian defect added to a Hermitian lattice induces an extensive number of states with scale-free localization. Furthermore, we demonstrate that, in a lattice with a parity-time-symmetric non-Hermitian defect, the scale-free localization emerges because of spontaneous parity-time symmetry breaking. Our results uncover a new type of localized states and extend the study of defect physics to the non-Hermitian regime.

cond-mat.mes-hall↗