Thermal Casimir Force Imaging of Nonequilibrium Hot Electrons

Weikang Lu; Ziyi Xu; Hewan Zhang; Svend Age Biehs; Achim Kittel; Ludi Qin; Xue Gong; Huanyi Xue; Yanru Song; Zhengyang Zhong; Shiyou Chen; Kun Ding; Wei Lu; Zhenghua An

arXiv · 2602.24157

Thermal Casimir Force Imaging of Nonequilibrium Hot Electrons

Weikang Lu·Ziyi Xu·Hewan Zhang·Svend Age Biehs·Achim Kittel·Ludi Qin·Xue Gong·Huanyi Xue·Yanru Song·Zhengyang Zhong·Shiyou Chen·Kun Ding·Wei Lu·Zhenghua An

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Abstract

The thermal Casimir effect, arising from fluctuating electromagnetic fields of thermally agitated charges, induces thermosensitive forces and presents a novel approach to detecting nanoscale hot electrons, elusive yet ubiquitous in modern miniaturized transistors. However, detecting thermal Casimir forces at the nanoscale remains extremely challenging due to background forces such as electrostatic force and quantum Casimir force. In this study, we present the first non-contact force measurement of hot electrons based on the thermal Casimir effect. Using an atomic force microscope (AFM) with a dual-resonant tip, we achieve thermosensitive force detection of nonequilibrium hot electrons while effectively suppressing background thermo-insensitive forces, thereby distinguishing them from cold electrons. In silicon nanoconstriction devices, the measured thermal Casimir pressure reaches approximately 3 bar at a separation of 5 nm at an electron temperature of about 10^3 K. Our work introduces a novel methodology for hot electron nanothermometry and provides critical insights into the thermo-mechanical properties of post-Moore nanoelectronics.

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Weikang Lu, Ziyi Xu, Hewan Zhang, Svend Age Biehs, Achim Kittel, Ludi Qin, Xue Gong, Huanyi Xue, Yanru Song, Zhengyang Zhong, Shiyou Chen, Kun Ding, Wei Lu, Zhenghua An. 2026-02-27. Thermal Casimir Force Imaging of Nonequilibrium Hot Electrons. https://arxiv.org/abs/2602.24157

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