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Fluctuation-induced Hall-like lateral forces in a chiral-gain environment

Daigo Oue1,2,3,* and Mário G. Silveirinha1

  • *Contact author: daigo.oue@gmail.com
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Phys. Rev. Research 8, 013158 – Published 11 February, 2026

DOI: https://doi.org/10.1103/rxkz-gv78

Abstract

Here, we demonstrate that vacuum fluctuations can induce lateral forces on a small particle positioned near a translation-invariant uniform non-Hermitian substrate with chiral gain. This type of non-Hermitian response can be engineered by biasing a low-symmetry conductor with a static electric field and is rooted in the quantum geometry of the material through the Berry curvature dipole. The chiral-gain material acts as an active medium for a particular circular polarization handedness, while serving as a passive, dissipative medium for the other polarization handedness. Owing to the nonreciprocity and gain characteristics, momentum is continuously exchanged in a preferred direction parallel to the surface between the test particle and the surrounding electromagnetic field, giving rise to lateral forces. Interestingly, the force can be viewed as a fluctuation-induced drag analogous to a Hall force. Indeed, although the gain is driven by an electric current, the resulting force acts perpendicular to the bias—unlike conventional current-drag effects. This effect stems from the skewed propagation characteristics of surface modes and gain-momentum locking. Our theory reveals a Hall-like asymmetry in the field correlations and establishes a link between quantum geometry and fluctuation-induced phenomena, offering possibilities for nanoscale control via tailored electromagnetic environments.

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Phys. Rev. Research 8, 013158– Published 11 February, 2026
  • Received 27 July 2025
  • Accepted 10 January 2026
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