Among the most intriguing features of non-Hermitian (NH) systems is the ability of complex
energies to form braids under parametric variation. Several braiding behaviors, including …

Eigenstate coalescence in non-Hermitian systems is widely observed in diverse scientific
domains encompassing optics and open quantum systems. Recent investigations have …

Non-Hermitian systems have Riemann surface structures of complex eigenvalues that admit
singularities known as exceptional points. Combining with geometric phases of eigenstates …

Topologically ordered phases have robust degenerate ground states against the local
perturbations, providing a promising platform for fault-tolerant quantum computation. Despite …

The complex eigenenergies and non-orthogonal eigenstates of non-Hermitian systems
exhibit unique topological phenomena that cannot appear in Hermitian systems …

We investigate the topological properties of multiple exceptional points in non-Hermitian two-
level systems, emphasizing vorticity as a topological invariant arising from complex energy …

Eigenstate coalescence in non-Hermitian systems is widely observed in diverse scientific
domains encompassing optics and open quantum systems. Recent investigations have …

This work reviews the state of the art for high order perturbation method for parametric
eigenvalue problems and propose some extensions for the multiparameters case. This …

In this work, a new method is presented in order to locate high order exceptional points (EP)
arising in eigenvalue problems. EP correspond to a particular tuning of some complex …