In this paper, we demonstrate that the non-Hermiticity can induce reentrant localization in a generalized quasiperiodic lattice. Specifically, by considering a nonreciprocal dimerized lattice with staggered quasiperiodic disorder, we find that the localization transition can appear twice by increasing the disorder strength. We also unravel a multi-complex-real eigenenergy transition, whose transition points coincide with those in the localization phase transitions. Moreover, the impacts of boundary conditions on the localization properties have been clarified. Finally, we study the wavepacket dynamics in different parameter regimes, which offers an experimentally feasible route to detect the reentrant localization.

The diffraction pattern of a two-dimensional optically induced atomic lattice is reported experimentally in a three-level atomic system. Such a two-dimensional optical lattice is established by two orthogonal standing-wave fields induced by the interference of two pairs of coupling laser beams. When the probe beam is launched into it, a spatially modulated discrete diffraction pattern can be obtained at the output plane of the vapor cell under the electromagnetically induced transparency condition. We investigate the diffraction pattern under different experimental parameters and find that it can be effectively controlled by tuning the coupling laser power and two-photon detuning. Our work may potentially pave the way for studying the control of light and other intriguing physical phenomena based on such a periodically modulated atomic lattice.

Continuum Landau modes — predicted recently in a non-Hermitian Dirac Hamiltonian under a uniform magnetic field — are continuous bound states with no counterparts in Hermitian systems. However, they have still not been confirmed in experiments. Here, we report an experimental observation of continuum Landau modes in non-Hermitian electric circuits, in which the non-Hermitian Dirac Hamiltonian is simulated by non-reciprocal hoppings and the pseudomagnetic field is introduced by inhomogeneous complex on-site potentials. Through measuring the admittance spectrum and the eigenstates, we successfully verify key features of continuum Landau modes. Particularly, we observe the exotic voltage response acting as a rainbow trap or wave funnel through full-field excitation. This response originates from the linear relationship between the modes’ center position and complex eigenvalues. Our work builds a bridge between non-Hermiticity and magnetic fields, and thus opens an avenue to explore exotic non-Hermitian physics.

The edge-to-edge topological transport of the one-dimensional odd-sized Su-Schrieffer-Heeger model plays a crucial role in robust energy transfer and information processing. However, it has not been verified experimentally. Here we report on an experimental demonstration of this topological transport in a one-dimensional photonic lattice of coupled waveguides. When slowly varying the spacings of the adjacent waveguides, the robust topological transport of light from the leftmost to the rightmost channels has been successfully observed. Moreover, the transport speed and efficiency of light are enhanced considerably by introducing the exponential-type modulations of the coupling strengths. The experimental results agree well with analytical calculations and numerical simulations. This transport of light observed may serve as the basis for photonic devices of unconventional functions.

A novel tunable all-optical grating is realized experimentally in a V + Ξ configuration coherent rubidium thermal vapor. This new energy level structure employs a Rydberg level as the uppermost level and contains two typical electromagnetically induced transparency energy level configurations with the same probe field. Compared with the traditional V-type three-level grating, a significant improvement of the diffraction efficiency of this novel grating was observed. Its improvement was then also demonstrated experimentally by the transition spectrum and theoretically by a comprehensive simulation. The diffraction efficiency gain introduced by the control laser field was tuned with several experimental parameters, such as the atomic density and the control field intensity. And the maximum enhancement rate of first-order diffraction efficiency is proved to be as high as 30%. Such a novel all-optical tunable grating promises to be the new driving force in the advancement of all-optical communications and information technology.