New technologies and materials with superior characteristics impel great development of functional devices in the terahertz field. The dynamically tunable plasmon-induced transparency (PIT) based on radiative–radiative-coupling in terahertz hybrid metal–graphene metamaterial is numerically investigated in this paper. For the active manipulation of the PIT device, the single-layer graphene is integrated into the proposed structure consisting of the split-ring-resonator (SRR) and the closed-ring-resonator (CRR). Dynamically adjusting Fermi energy in graphene leads to modulation of the PIT window, allowing for the active control of the group delay. From the simulated electrical field distributions and effective circuit model to analyze, the transmission spectrum modulation can be attributed to the altering in the energy loss of the dark mode resonator through the conduction effect of the graphene layer. Our work offers theoretical references for the development of slow light terahertz devices in the future.

The combination of graphene and metamaterials is the ideal route to achieve active control of the electromagnetic wave in the terahertz (THz) regime. Here, the tunable plasmon-induced transparency (PIT) metamaterial, integrating metal resonators with tunable graphene, is numerically investigated at THz frequencies. By varying the Fermi energy of graphene, the reconfigurable coupling condition is actively modulated and continuous manipulation of the metamaterial resonance intensity is achieved. In this device structure, monolayer graphene operates as a tunable conductive film which yields actively controlled PIT behavior and the accompanied group delay. This device concept provides theoretical guidance to design compact terahertz modulation devices.

Recently, two-dimensional (2D) half-topological states, emerging in 2D half Weyl semimetals and half Chern insulators, have attracted much attention due to their promising applications in spintronics. The fully spin-polarized topological nontrivial bands near the Fermi level give rise to spin-resolved bulk and boundary charge currents, which might be beneficial to the charge transfer in catalytic reactions. Taking the room temperature ferromagnetic (FM) TiTe monolayer (T _C ∼965 K) as an example, the hydrogen evolution reaction (HER) performance was studied by first-principles calculations. The Gibbs free energy ΔG_H* of the hollow site surrounded by Ti atoms (hollow@Ti) is evaluated as −0.06 eV, approaching that of Pt (−0.09 eV). The corresponding activation energies of the Tafel and Heyrovsky reactions are estimated to be 0.92 and 1.32 eV, respectively, which are comparable to MoS₂ (1.0–1.5 eV). In addition, the calculation results indicate that ΔG_H* is robust against the magnetization direction and is linearly related to the biaxial strain ranging from −3% to 3%. This work uncovers the efficient HER performance of room temperature FM TiTe monolayers, and provides new insights into the design of catalysts based on half Weyl semimetals and half Chern insulators.

The introduction of graphene into metamaterials allows for more flexible and convenient control of electromagnetic waves. In this paper, one simple plasmon-induced transparency (PIT) structure with tunability and polarization independence is investigated in the terahertz (THz) regime. The simulation results indicate that the transparent window can be manipulated in a wide range and even switched off by merely changing the Fermi energy of graphene. By continuously altering the resonance intensity of the dark resonator using the graphene, the PIT resonance can be actively manipulated. The behavior can be elucidated by the classical coupled two-particle model, which corresponds well to the simulation results. Owing to the fourfold symmetric structure, the proposed PIT device exhibits polarization-independent characteristics. This work provides design guidance for metal-graphene THz modulators.

In recent years, the active control of terahertz waves using artificial microstructures has attracted increasing attention, especially toward the ones that have multiple plasmon-induced transparency (PIT) responses. Here, a homogeneous graphene-metal metasurface, exhibiting tunable dual-PIT in its terahertz (THz) spectral response, is investigated numerically and theoretically. Individual and simultaneous control of the two PIT transmission windows and the two slow-light effects are achieved by reconstructing the Fermi energies of the graphene strips. The modulation behavior can be expounded by the classical coupled three-particle model, which is confirmed by the simulation results. Moreover, the electric field distribution is introduced to analyze the dual-PIT active modulation mechanism. This work provides theoretical guidance for versatile applications in multi-function terahertz switches and slow-light devices.

We study the transport of the Josephson current in one-dimensional SF1F2F3S junctions, where S represents s-wave superconductors and F1, F2, and F3 denote ferromagnets with noncollinear magnetizations. The Josephson current displays distinct characteristics under various magnetization configurations as we vary the exchange fields (h1, h3) and thicknesses (d1, d3) of the F1 and F3 layers. Building on Eschrig's conversion mechanisms [Eschrig, Phys. Today 64(1), 43 (2011) and Eschrig, Rep. Prog. Phys. 78, 104501 (2015)], we rigorously derive the conversion and transport processes of spin-singlet and spin-triplet Cooper pairs as they traverse the ferromagnetic trilayers, which helps clarify the observed variations in the Josephson current. We demonstrate that opposite-spin Cooper pairs acquire an additional phase of Qjdj upon passing through each Fj layer (j = 1, 3). Here, Qj = 2hj/(ℏvF) represents the center-of-mass momentum of the Cooper pairs, where vF is the Fermi velocity. This result aligns with the description of these pairs provided in Eq. (73) of Eschrig [Rep. Prog. Phys. 78, 104501 (2015)]. The contributions of Qjdj to the Josephson current depend on the exchange field of the F2 layer and the magnetization directions of the F1 and F3 layers. When the F2 layer is a ferromagnet, the azimuthal angle difference (χ3 − χ1) between the F1 and F3 layers modulates the current amplitude. This angular difference has been previously discussed in Grein et al. [Phys. Rev. Lett. 102, 227005 (2009)] and Eschrig [Rep. Prog. Phys. 78, 104501 (2015)], and it has more recently been examined in detail in Schulz et al. [Phys. Rev. B 112, 104514 (2025) and Phys. Rev. B 112, 104515 (2025)]. In contrast, when the F2 layer is a half-metal, this angle difference induces a phase shift in the current without affecting its amplitude, consistent with the results presented in Eschrig and Löfwander [Nat. Phys. 4, 138 (2008)]. These findings open new possibilities for controlling long-range Josephson currents in practical applications.