Toward Single-Photon Detection with Superconducting Niobium Diselenide Nanowires

We present superconducting nanowire photodetectors based on hBN-encapsulated, few-layer NbSe₂, showing signatures of single-photon sensitivity. The top-down fabrication process preserves the superconducting properties of NbSe₂, as confirmed by low-temperature transport measurements showing comparable results to unpatterned sheets, and it maintains a contact and wiring resistance down to ∼30 Ω at T = 4 K. Meandered NbSe₂ nanowires exhibit high responsivity (up to 4.9 × 10⁴ V/W) over a spectral range of 650–1550 nm in a closed-cycle cryostat at 4 K, outperforming samples with different geometries in this work. The meander achieves a recovery time of (135 ± 36) ns, a system timing jitter of (1103 ± 7) ps, and a detection efficiency of ∼0.01% at 0.95I_c. A linear increase of the count rate with the number of photons between the noise level and the latching threshold offers a signature of single-photon sensitivity at 1100 nm.