Abstract
We propose an application of a parity-time symmetric non-Hermitian Su-Schrieffer-Heeger (SSH) model by embedded it in a two-dimensional square lattice tube. The coalescence state at the exceptional point of non-Hermitian SSH model is chiral and selectively controls helical transport and amplification. Two typical helicity-dependent scattering dynamics are observed. If the incidence has an identical helicity with the embedded non-Hermitian SSH model, we observe a perfect transmission without reflection. However, if the incidence has an opposite helicity with the embedded non-Hermitian SSH model, except for a full transmission, we observe an amplified transmission with different helicity from the incidence; but the amplified reflection has identical helicity with the incidence. These intriguing features are completely unexpected in Hermitian system. Moreover, the helical amplification at high efficiency can be triggered by an arbitrary excitation. The different dynamics between incidences with opposite helicities are results of unidirectional tunneling, which is revealed to be capable of realizing without introducing magnetic field. Our findings open a direction in all-optical device and provide perspectives in non-Hermitian transport.
Highlights
Nowadays non-Hermitian physics has emerged as a versatile platform for the exploring of functional devices that are absent or difficult to realize in a Hermitian regime [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]
We propose an application of the PT -symmetric non-Hermitian Su-Schrieffer-Heeger (SSH) model at the exceptional point (EP) [47,48,49,50,51,52,53], which exhibits unidirectionality
We propose the helical transport controlled by a PT -symmetric non-Hermitian SSH ring at the EP as a helical filter
Summary
Nowadays non-Hermitian physics has emerged as a versatile platform for the exploring of functional devices that are absent or difficult to realize in a Hermitian regime [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]. The unidirectionality leads to the helicity dependent dynamics of wave propagation. The non-Hermitian SSH ring is embedded in a square lattice tube center as a scattering center. The non-Hermitian SSH ring at the EP leads to two typical helicity-dependent scattering behaviors: (i) zero transverse bandwidth perfect transmission without reflection and (ii) amplified zero transverse bandwidth interfered transmission with reflection. This dramatically differs from the traditional helical scattering that transmission after scattering has identical helicity with the incidence, but the reflection has opposite helicity with the incidence These features are useful for the control of helical transport and amplification.
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