Non-Bloch Theory for Spatiotemporal Photonic Crystals Assisted by Continuum Effective Medium

As one indispensable type of nonreciprocal mechanism, a system with temporal modulations is intrinsically open in the physical sense and inevitably non-Hermitian, but the space and time degrees of freedom are nonseparable in a large variety of circumstances, which restrains the non-Bloch band theory to apply. Here, we investigate the spatially photonic crystals (PhCs) composed of spatiotemporal modulation materials (STMs) and homogeneous media, dubbed as the STM-PhC, wherein the spatial and temporal modulations are deliberately designed to be correlated. To bypass the difficulty of the spatiotemporal correlation, we first employ the effective medium theory to account for the dispersion of fundamental bands under the influence of Floquet sidebands. Based on the dynamical degeneracy splitting viewpoint and continuum generalized Brillouin zone condition, we then analytically give the criteria for the existence of the non-Hermitian skin effect in the STM. Assisted by developing a numerical method that embeds the plane wave expansion in the transfer matrix, we establish the non-Bloch band theory for the low-frequency Floquet bands in the STM-PhCs, in which the central is the identification of the generalized Brillouin zone. We finally delve into the topological properties, including non-Bloch Zak phases and delocalization of topologically edge states. Our work validates that effective medium assists the non-Bloch band theory applied to the STM-PhCs, which delivers a prescription to broaden the horizons of non-Bloch theory

Tuning and Identification of Interband Transitions in Monolayer and Bilayer Molybdenum Disulfide Using Hydrostatic Pressure

Few-layer molybdenum disulfide (MoS₂) is advantageous for application in next-generation electronic and opto­electronic devices. For monolayer MoS₂, it has been established that both the conduction band minimum (CBM) and the valence band maximum (VBM) occur at the K point in the Brillouin zone. For bilayer MoS₂, it is known that the VBM occurs at the Γ point. However, whether the K valley or the Λ valley forms the CBM and the energy difference between them remain disputable. Theoretical calculations have not provided a conclusive answer. In this paper, we demonstrate that a direct K–K to an indirect Λ–K interband transition in bilayer MoS₂ can be optically detected by tuning the hydrostatic pressure. A changeover of the CBM from the K valley to the Λ valley is observed to occur under a pressure of approximately 1.5 GPa. The experimental results clearly indicate that the K valley forms the CBM under zero strain, while the Λ valley is approximately 89 ± 9 meV higher in energy

Probing Spin–Orbit Coupling and Interlayer Coupling in Atomically Thin Molybdenum Disulfide Using Hydrostatic Pressure

In two-dimensional transition-metal dichalcogenides, both spin–orbit coupling and interlayer coupling play critical roles in the electronic band structure and are desirable for the potential applications in spin electronics. Here, we demonstrate the pressure characteristics of the exciton absorption peaks (so-called excitons A, B and C) in monolayer, bilayer, and trilayer molybdenum disulfide (MoS₂) by studying the reflectance spectra under hydrostatic pressure and performing the electronic band structure calculations based on density functional theory to account for the experimental observations. We find that the valence band maximum splitting at the K point in monolayer MoS₂, induced by spin–orbit coupling, remains almost unchanged with increasing pressure applied up to 3.98 GPa, indicating that the spin–orbit coupling is insensitive to the pressure. For bilayer and trilayer MoS₂, however, the splitting shows an increase with increasing pressure due to the pressure-induced strengthening of the interlayer coupling. The experimental results are in good agreement with the theoretical calculations. Moreover, the exciton C is identified to be the interband transition related to the van Hove singularity located at a special point which is approximately 1/4 of the total length of Γ–K away from the Γ point in the Brillouin zone

Nanocorrugation-Induced Forces between Electrically Neutral Metallic Objects

Recent advances in nanotechnology have created tremendous excitement across different disciplines, but in order to fully control and manipulate nanoscale objects, we must understand the forces at work at the nanoscale, which can be very different from those that dominate the macroscale. We show that there is a kind of curvature-induced force that acts between nanocorrugated electrically neutral metallic surfaces. Absent in flat surfaces, such a force owes its existence entirely to geometric curvature and originates from the kinetic energy associated with the electron density, which tends to make the profile of the electron density smoother than that of the ionic background and hence induces curvature-induced local charges. Such a force cannot be found using standard classical electromagnetic approaches, and we use a self-consistent hydrodynamics model as well as first-principles density functional calculations to explore the character of such forces. These two methods give qualitatively similar results. We found that the force can be attractive or repulsive, depending on the details of the nanocorrugation, and its magnitude is comparable to light-induced forces acting on plasmonic nano-objects

Functional performance in the pilot-scale wastewater treatment system over 345 days.

<p>(a) Influent and effluent BOD concentrations. (b) Influent and effluent ammonia concentrations. (c) Effluent nitrate concentrations.</p

Histograms of T-RF relative abundances in the system for <i>Taq</i>I T-RFLP profiles.

<p>The relative abundance is the ratio of the peak area of a given T-RF in a given sample to the sum of all T-RFs in that sample expressed as a percentage. Arrows indicate the sizes of the restriction fragments for the abundant T-RFs in base pairs.</p

The anatomical distribution of the altered normalized ReHo in anisometropic amblyopia visualized by individuals Caret v5.61 software (<i>P<0.01</i>, 130 voxels, Alphasim corrected <i>P_alpha</i> = 0.01).

<p>Abbreviations: Pcun = precuneus, IFG = inferior frontal gyrus, MPFC = media prefrontal cortex, Cereb = cerebellum; PostCG = postcentral gyrus, PretCG = precentral gyrus, PCL = paracentral lobule, STG = superior temporal gyrus, FG = fusiform gyrus, MOG = middle occipital gyrus.</p

Plot of the normalized ReHo values in the brain areas in which ReHo values were significantly different between the subjects with normal vision and anisometropic amblyopia individuals(A).

<p>Correlation between the mean fitted ReHo indices and visual acuities in the patients with anisometropic amblyopia (P<0.05)(B). Abbreviations: same with <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0043373#pone-0043373-g001" target="_blank">Figure 1</a>.</p

Brain areas with increased ReHo in anisometropic amblyopia individuals (<i>P<0.01</i>, 130 voxels, Alphasim corrected <i>P_alpha</i> = 0.01).

<p>Abbreviations: PostCG = postcentral gyrus, PretCG = precentral gyrus, PCL = paracentral lobule, INS/PUT = insula and putamen, STG = superior temporal gyrus, FG = fusiform gyrus, MOG = middle occipital gyrus.</p><p>L: left, R: right.</p

Moving-window analysis based on AOB T-RFLP profiles.

<p>Each data point is the change percentage between the bacterial communities of 2 consecutive dates. The time span between two consecutive dates is 15 days.</p