Unveiling van Hove Singularity-Boosted Photothermoelectric Response for Wearable Human-Radiation Detection

Van Hove singularity (vHs), the singularity point of density of states (DOS) in crystalline solids, is a research hotspot in emerging phenomena such as light-matter interaction, superconducting, and quantum anomalous Hall effect. Although the significance of vHs in photothermoelectric (PTE) effect has been recognized, its integral role in electron excitation and thermoelectric effect is still unclear, particularly in the mid-infrared band that suffers from Pauli blockade in semimetals. Here, we unveil the Fermi-level-modulated PTE behavior in the vicinity of vHs in carbon nanotubes, employing ionic-liquid gating. The concurrent enhancement of optical absorption and thermoelectric effect effectively improves the overall photoresponse by tens of folds at the vHs point. Generally applicable to strongly correlated systems such as metallic 1D nanomaterials and 2D Moiré systems, a quantitative correlation between PTE photodetectivity and electronic DOS is derived in the vicinity of the vHs point. Finally, chemically doped PTE mid-infrared detectors with graded doping levels are demonstrated to exhibit human-radiation sensitivity, high flexibility, and high transparency, paving the way for wearable sensor networks in healthcare systems and the Internet of Things.