17 research outputs found
Helical damping and anomalous critical non-Hermitian skin effect
Non-Hermitian skin effect and critical skin effect are unique features of
non-Hermitian systems. In this Letter, we study an open system with its
dynamics of single-particle correlation function effectively dominated by a
non-Hermitian damping matrix, which exhibits skin effect, and
uncover the existence of a novel phenomenon of helical damping. When adding
perturbations that break anomalous time reversal symmetry to the system, the
critical skin effect occurs, which causes the disappearance of the helical
damping in the thermodynamic limit although it can exist in small size systems.
We also demonstrate the existence of anomalous critical skin effect when we
couple two identical systems with skin effect. With the help of
non-Bloch band theory, we unveil that the change of generalized Brillouin zone
equation is the necessary condition of critical skin effect.Comment: 7+5 pages, 4+5 figure
Dynamical Degeneracy Splitting and Directional Invisibility in Non-Hermitian Systems
In this paper, we introduce the concept of dynamical degeneracy splitting to
describe the anisotropic decay behaviors in non-Hermitian systems. We
demonstrate that systems with dynamical degeneracy splitting exhibit two
distinctive features: (i) the system shows frequency-resolved non-Hermitian
skin effect; (ii) Green's function exhibits anomalous at given frequency,
leading to uneven broadening in spectral function and anomalous scattering. As
an application, we propose directional invisibility based on wave packet
dynamics to investigate the geometry-dependent skin effect in higher
dimensions. Our work elucidates a faithful correspondence between non-Hermitian
skin effect and Green's function, offering a guiding principle for exploration
of novel physical phenomena emerging from this effect.Comment: 24 pages, 11 figure
Edge theory of the non-Hermitian skin modes in higher dimensions
In this Letter, we propose a universal edge theory for the higher-dimensional
non-Hermitian edge-skin modes. In contrast to the well-understood corner-skin
effect, we demonstrate that the edge-skin effect requires the protection of
reciprocity or inversion. Through an exact mapping, we show that these skin
modes share the same bulk-edge correspondence as the Fermi-arc states in a
Hermitian Dirac semimetal. Based on this mapping, we introduce a bulk
projection criterion to identify the skin edge, and utilize the non-Bloch
Hamiltonian under specific cylinder geometry to characterize the localization
features of edge-skin modes. We find that the edge-skin modes are made of
components with real-valued momenta along the edge, and interestingly the decay
direction typically deviates from the normal direction of the edge, a
phenomenon we term skewness. Furthermore, we reveal the remarkable sensitivity
of the cylinder-geometry spectrum to disturbances that violate fragile
reciprocity. When this symmetry is disrupted, the cylinder-geometry spectrum
undergoes an abrupt transition towards the near open-boundary spectrum,
underscoring a key difference between corner-skin and edge-skin effects.Comment: 15 pages, 8 figure