The design of tunable and multifunctional metastructures (MSs) is currently a trend in the terahertz (THz) field. Based on the characteristic that thermal excitation can cause the phase transition of vanadium dioxide (VO2), a MS that concentrates both cross-polarization conversion and absorption functions is proposed in this paper, and switching two functions can be achieved by controlling the temperature. At high temperatures (68°C), the proposed MS exhibits a narrow-band absorption function in the range of 0.67 THz-0.95 THz. When the temperature drops below 68°C, VO2 is in the insulated state, and the structure can be considered as a polarization converter. Simulation results indicate that the broadband cross-polarization conversion can be realized in 0.69 THz-1.38 THz with a polarization conversion ratio above 90% and a relative bandwidth of 66.7%. This paper analyzes the amplitude, phase, and surface current distributions under the polarization conversion function, as well as the impedance, power loss distributions, and equivalent circuits under the absorption function. In addition, the angular stability and the influences of the structural parameters on performance are also discussed. The proposed MS is suitable for complex applications due to its tunability and dual functionality.
Neuromorphic computing is expected to achieve human-brain performance by reproducing the structure of biological neural systems. However, previous neuromorphic designs based on synapse devices are all unsatisfying for their hardwired network structure and limited connection density, far from their biological counterpart, which has high connection density and the ability of meta-learning. Here, we propose a neural network based on magnon scattering modulated by an omnidirectional mobile hopfion in antiferromagnets. The states of neurons are encoded in the frequency distribution of magnons, and the connections between them are related to the frequency dependence of magnon scattering. Last, by controlling the hopfion’s state, we can modulate hyperparameters in our network and realize the first meta-learning device that is verified to be well functioning. It not only breaks the connection density bottleneck but also provides a guideline for future designs of neuromorphic devices.
Based on the principle of Fabry–Perot (F–P) cavity resonance and the selective permeability of gratings to specific electromagnetic waves, a graphene‐based metastructure (MS) is proposed for transmissive polarization conversion (PC). Using the full‐wave numerical simulation, it is found that by varying the Fermi energy of graphene, the effective resonance range of the suggested MS can be dynamically adjusted from 0.47 to 0.348–0.714 THz, achieving the target of precise to ultra‐broadband polarization modulation. In this paper, the plausibility of the structure is verified from multiple perspectives, and the correlation analyses of the electric and magnetic fields are the supporting illustrations. Additionally, the triggering mechanism of PC is visually illustrated in the study of the surface currents distributions. Simulation results reveal that the MS is superior in performance, functionality, and principle, and it is foreseen to hold excellent promise for integrated equipment in the terahertz (THz) band.
The nodal topological superconducting (NTSC) state with Majorana flat bands (MFBs) is an exotic matter of state hosting Majorana fermions that obey non‐Abelian statistics. Recently, monolayer Ising superconductor NbSe2 is shown to be an ideal platform for realizing an NTSC state. Through tight‐binding calculations based on the Bogoliubov–de–Gennes Hamiltonian, it is demonstrated that the in‐plane magnetic field B combined with superconducting pairing Δs, Rashba spin–orbit coupling (SOC) Vr, and chemical potential μ can regulate the topological properties of the NTSC state. First, B larger than Δs effectively induces an NTSC state with nodal points (NPs) located on the high‐symmetry line of the Brillouin zone. The length of the resulting MFBs in the ribbon increases with B. Second, Rashba SOC greatly affects the number and locations of NPs by tilting bands near Fermi level (EF), leading to unidirectional Majorana edge states. Finally, when B > Δs, μ affects the bulk band structure at EF, resulting in an NTSC state with 6, 12, 18, 24 NPs and 0, 2, 3, 4 MFBs. These results are important to clarifying the behavior of the NTSC state under a B and designing a quantum computing platform based on exotic Majorana fermions.
Since the discovery of graphene in the atomic thin layer format, many investigations have been conducted to search for two-dimensional (2D) layered materials, in which 3d-transition metals offer many new...
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