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

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Van Hove singularities (vHs) are critical points in the density of states (DOS) of solids, influencing phenomena like superconductivity and light-matter interactions.
• The role of vHs in photothermoelectric (PTE) effects, especially in the mid-infrared spectrum affected by Pauli blockade, remains underexplored.
• Carbon nanotubes offer a promising platform for studying vHs due to their unique electronic properties.

Purpose of the Study:

• To investigate the Fermi-level-modulated photothermoelectric (PTE) behavior near Van Hove singularities (vHs) in carbon nanotubes.
• To elucidate the integral role of vHs in electron excitation and thermoelectric effects for mid-infrared detection.
• To establish a quantitative correlation between PTE photodetectivity and electronic DOS near vHs.

Main Methods:

• Utilized ionic-liquid gating to precisely control the Fermi level in carbon nanotubes.
• Investigated optical absorption and thermoelectric properties in the vicinity of vHs.
• Derived a quantitative correlation between PTE photodetectivity and electronic DOS.

Main Results:

• Demonstrated a significant enhancement (tens of folds) in photoresponse at the vHs point due to concurrent improvements in optical absorption and thermoelectric effects.
• Established a general applicability of the findings to strongly correlated systems, including 1D nanomaterials and 2D Moiré systems.
• Developed chemically doped PTE mid-infrared detectors with graded doping, showing human-radiation sensitivity, flexibility, and transparency.

Conclusions:

• Fermi-level modulation near vHs is a key strategy for optimizing PTE effects in carbon nanotubes and similar materials.
• The derived correlation provides a predictive tool for designing high-performance PTE detectors.
• The developed flexible and transparent detectors hold potential for wearable sensor networks in healthcare and IoT applications.