State-of-the-art metallic terahertz (THz) emitters rely predominantly on spintronic heterostructures, where heavy metals serve as passive spin-to-charge converters. Here, we demonstrate efficient THz radiation from standalone Pt nanofilms at cryogenic temperatures and under external magnetic fields. The governing mechanism is identified as the ultrafast photo-Nernst effect, wherein a transient thermal gradient drives a transverse charge current. The THz emission polarity is directly dictated by the sign of the Nernst coefficient, as verified by the phase reversal observed between Pt and W or Ta. Remarkably, both thickness scaling and alloying-induced suppression of thermal conductivity independently amplify the single-layer emission to levels comparable with benchmark spintronic bilayers. These findings redefine the established role of heavy metals from passive spin-sinks to active THz emitters, uncovering a universal emission paradigm applicable across diverse spintronic and quantum materials.
@article{arxiv.2603.21924,
title = {Efficient photo-Nernst terahertz emission in single heavy-metal films},
author = {Lei Wang and Linxuan Song and Elbert E. M. Chia and Peijie Sun and Jianlin Luo and Rongyan Chen and Yong-Chang Lau and Xinbo Wang},
journal= {arXiv preprint arXiv:2603.21924},
year = {2026}
}