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Fundamental and second-subharmonic Autler-Townes splitting in classical systems

Ahmed A. Barakat1,2,3,4,*, Avishek Chowdhury1, Anh Tuan Le1, and Eva M. Weig1,3,4

  • *Contact author: ahmed.barakat@tum.de
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Phys. Rev. A 113, 042223 – Published 24 April, 2026

DOI: https://doi.org/10.1103/m4m8-fkrr

Abstract

The dynamic Stark effect and Autler-Townes splitting (ATS) are hallmarks of driven two-level systems. We establish a direct correspondence between these quantum phenomena and the parametric normal mode splitting in coupled classical oscillators. This identifies a second-subharmonic ATS under a two-tone parametric drive. We find excellent agreement between the theory and the vibrations of a nanomechanical two-mode system, capturing both the fundamental and second-subharmonic ATS, and allowing quantitative extraction of the modal coupling irrespective of the degree of modal hybridization.

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Phys. Rev. A 113, 042223– Published 24 April, 2026
  • Received 15 December 2025
  • Accepted 12 March 2026
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