Cai-Zhen Li

Reconfigurable infrared plasmons are central to emerging nanophotonic technologies, yet their practical impact remains constrained by limited tuning bandwidth, poor reversibility, and material-specific spectral windows. Here we demonstrate ultrabroadband and fully reversible tuning of infrared plasmons in metallic van der Waals NbSe2 films enabled by gate-controlled lithium-ion intercalation. Ion intercalation provides a unique pathway to simultaneously modulate free-carrier density and screening from high-energy interband transitions, jointly reshaping both plasmon frequency and oscillator strength. As a result, plasmon resonances can be continuously swept over an unprecedented spectral span exceeding 5500 cm–1 within a single material platform, covering the telecom, mid-infrared and thermal far-infrared region. Leveraging this broad and reversible tunability, we realize electrically tunable wavelength-selective thermal emitters and thermal display patterns through plasmon-mediated emissivity modulation. Our results establish ion-intercalated van der Waals metals as a versatile and programmable platform for ultrabroadband tunable infrared nanophotonics and reversible thermal-radiation control.

Coupling topological surface states with superconductivity provides a powerful route to realizing a topological superconducting phase that can host Majorana zero modes and support fault-tolerant topological quantum computation. Here, we report proximity-induced two-dimensional superconductivity in a TaIrTe4/NbSe2 heterostructure, where superconductivity is induced into the surface of the type-II Weyl semimetal TaIrTe4. Differential resistance spectra reveal pronounced subgap oscillations, indicating multiple induced superconducting gaps associated with the coexistence of electron and hole Fermi pockets in TaIrTe4. The induced superconductivity exhibits strong anisotropy: while a modest out-of-plane magnetic field is sufficient to suppress the superconducting state, the in-plane upper critical field remains much higher and exceeds the Pauli limit below 2.7 K. Angular-dependent upper critical field measurements reveal a distinct Tinkham-like cusp, together with the Berezinskii–Kosterlitz–Thouless transition, confirming the two-dimensional nature of the induced superconductivity. These results establish TaIrTe4/NbSe2 heterostructure as a versatile platform for exploring superconductivity mediated by topological surface states in type-II Weyl systems.

The magnetic field-free Josephson diode effect (JDE) offers a promising route toward nonreciprocal superconducting devices, yet its microscopic origin and effective control remain unclear. Here, we demonstrate a tunable field-free JDE in NbSe₂/Nb₃Cl₈/NbSe₂ van der Waals (vdW) Josephson junctions. By reducing the Nb₃Cl₈ barrier thickness from four-layer to monolayer, the diode efficiency is significantly enhanced from 1.75% to 20.88%. Moreover, the diode efficiency can be effectively modulated by an out-of-plane electric field, indicating the presence of intrinsic electric polarization in the junction. Both thickness variation and electric field tuning modify the polarization strength, thereby enabling broad control of the diode efficiency. These results uncover the crucial role of intrinsic electric polarization in realizing the field-free JDE and establish this effect as a sensitive probe of spontaneous time-reversal symmetry breaking in superconducting heterostructures.

Bi₄Br₄ is a quasi-one-dimensional van der Waals topological insulator with novel electronic properties. Several efforts have been devoted to the understanding of its bulk form, yet it remains a challenge to explore the transport properties in low-dimensional structures due to the difficulty of device fabrication. Here we report for the first time a gate-tunable transport in exfoliated Bi₄Br₄ nanobelts. Notable two-frequency Shubnikov–de Haas oscillations oscillations are discovered at low temperatures, with the low- and high-frequency parts coming from the three-dimensional bulk state and the two-dimensional surface state, respectively. In addition, ambipolar field effect is realized with a longitudinal resistance peak and a sign reverse in the Hall coefficient. Our successful measurements of quantum oscillations and realization of gate-tunable transport lay a foundation for further investigation of novel topological properties and room-temperature quantum spin Hall states in Bi₄Br₄.