2018/09/30 by Sachiko Nakamura, Yudai Iida, Yuta Murotani +3 · 74 citations
Physics and Astronomy · #Advanced Chemical Physics Studies #Amplitude #Charge (physics) #Condensed matter physics #Field (mathematics) #Higgs boson #Josephson effect #Physics #Physics of Superconductivity and Magnetism #Quantum and electron transport phenomena #Quantum mechanics #Superconductivity #Supercurrent #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevlett.122.257001
published in Physical Review Letters 122(25), 257001 (American Physical Society) · 5 pages, 4 figures
arxiv created 2019/06/16 · openalex publication_date 2019/06/25 · arxiv updated 2019/07/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The Higgs mode in superconductors, i.e., the collective amplitude mode of the order parameter, does not associate with charge nor spin fluctuations, therefore it does not couple to the electromagnetic field in the linear response regime. Contrary to this common understanding, here, we demonstrate that if the dc supercurrent is introduced into the superconductor, the Higgs mode becomes infrared active and is directly observed in the linear optical conductivity measurement. We observed a sharp resonant peak at ω=2Δ in the optical conductivity spectrum of a thin-film NbN in the presence of dc supercurrent, showing a reasonable agreement with the recent theoretical prediction. The method as proven by this work opens a new pathway to study the Higgs mode in a wide variety of superconductors.