Ultra-Broadband Negative Photoconductivity in a Van der Waals Ferromagnetic Metal FePd₂Te₂

Negative photoconductivity (NPC) in low-dimensional materials has attracted considerable interest for its potential in novel optoelectronic devices. Here, we report an ultra-broadband NPC response in FePd₂Te₂, a van der Waals ferromagnet, spanning from visible to long-wavelength infrared at room temperature. The device achieves a responsivity of ~4.9 A/W and external quantum efficiency of ~240% at 2500 nm, with a noise-equivalent power (NEP) below 3.0 × 10^-15 W/Hz^1/2 and a specific detectivity (D*) exceeding 3.6 × 10¹¹ cmHz^1/2/W across the infrared range. Systematic measurements identify the photobolometric effect as the underlying mechanism, wherein wavelength-dependent absorption depths play a key role in shaping the photoresponse characteristics. These results establish FePd₂Te₂ as a promising platform for uncooled broadband infrared detection and highlight the potential of magnetic van der Waals materials for future optoelectronics.