Field-enhanced terahertz spectroscopy serves as a powerful analytical tool for biochemical sensing, materials characterization, and medical diagnostics, where detection sensitivity fundamentally depends on electric field enhancement and confinement. However, the severe scale mismatch between long terahertz wavelengths (on the order of 100 $$\upmu$$ μ m) and nanoscale analytes (typically < 10 nm) imposes critical limitations on conventional far-field techniques. Here, we present a breakthrough sensing approach utilizing twisted double-layer graphene plasmonic metasurfaces (t-DL-GPMs) with nanometric dielectric spacers. Our investigations reveal that these t-DL-GPMs support strongly confined acoustic plasmon nanocavity modes featuring extraordinary field enhancement and deep subwavelength field concentration, along with an extremely small mode volume (10 ⁻¹³ λ ₀ ³ ). Compared to single-layer and untwisted double-layer graphene configurations, the twisted architecture demonstrates dramatically improved sensing performance, with figures of merit enhanced by factors of 22 and 48, respectively. Most significantly, the platform enables clear identification of terahertz vibrational fingerprints from molecular layers as thin as 1 nm. This work not only opens novel avenues for nanoscale terahertz detection, pushing the THz sensing into unprecedented deep-nano level, but also establishes a versatile foundation for exploring extreme light-matter interactions and developing advanced terahertz photonic devices.

Multiband and nodal-like superconductivity (SC) with s- + d-wave pairing symmetry have implied that tetragonal iron sulphide (FeS) is a distinctive testbed for exploring unexpected electronic correlations. In particular, the low-moment disordered static magnetism originating from the Fe moment leads to the possibility of the coexistence of magnetic orders (MOs) in the superconducting ground state via the tuning of electronic configurations. Here, guided by density functional theory (DFT) calculations, we found that slightly substitutionally doped chromium (Cr) atoms in tetragonal FeS single crystals can induce both considerable d-orbital reconstruction around the Fermi surface and a local magnetic moment of 2.4 µ_B at each doping site, which could highly modulate the SC ground states of the host. On this basis, a clear magnetic transition and reduced anisotropy of SC were experimentally observed. In particular, SC can survive with a doping content below 0.05. This coexistence of SC and MOs suggests strong spin correlations between Cr dopants and the host through exchange coupling. Further, an electronic temperature-related phase diagram of FeS with Cr doping contents from 0 to 0.07 is also provided. These results demonstrate that the continuous injection of local moments can be a controllable method to use to tune collective orders in unconventional iron-based superconductors.