Singular high-harmonic transport above a quantum threshold

Yugo Onishi; Su-Yang Xu; Liang Fu

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arXiv · 2609.20990

Singular high-harmonic transport above a quantum threshold

Yugo Onishi·Su-Yang Xu·Liang Fu

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Abstract

We show that Landau-Zener tunneling in a small-gap insulator produces a singular DC current--voltage relation, and correspondingly, strong high-harmonic generation in AC transport. Remarkably, high-harmonic responses decrease subexponentially with harmonic order, which is parametrically slower than in ordinary conductors and PN diodes. We further derive a scaling law for the current amplitude at frequency $nω$ produced by the applied electric field $E$ at fundamental frequency $ω$. Our work offers a promising route to THz generation based on frequency multiplication in solids.

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Yugo Onishi, Su-Yang Xu, Liang Fu. 2026-09-17. Singular high-harmonic transport above a quantum threshold. https://arxiv.org/abs/2609.20990

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