Terahertz range polarization rotation in the candidate time-reversal symmetry breaking superconductor BiNi

Fuente: arXiv
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Autores principales: Romero III, Ralph, Tagay, Zhenisbek, Liang, Jiahao, Yan, Jason Y., Yue, Di, Armitage, N. P.
Formato: Preprint
Publicado: 2025
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author Romero III, Ralph
Tagay, Zhenisbek
Liang, Jiahao
Yan, Jason Y.
Yue, Di
Armitage, N. P.
author_facet Romero III, Ralph
Tagay, Zhenisbek
Liang, Jiahao
Yan, Jason Y.
Yue, Di
Armitage, N. P.
contents Here we report the observation of time-reversal symmetry (TRS) breaking superconductivity in a BiNi bilayer using terahertz (THz) polarimetry. Leveraging a novel high-precision THz polarimetry technique, we detect, in the superconducting state and at zero magnetic field, the smallest polarization rotation of THz light measured to date. By using the MgO substrate itself as an optical resonator, we can reference the Faraday and Kerr rotations to each other. We observe a low-frequency Kerr rotation on the order of several hundred microradians in the superconducting phase, a clear signature consistent with TRS-breaking superconductivity. Our measurements enable direct access to the THz-range Hall conductivity. Through a Kramers-Kronig analysis, we link these low-energy measurements to prior high-frequency magneto-optic Kerr effect (MOKE) data. This connection provides critical insight into the nature of the TRS-breaking state, supporting a multiband superconducting scenario over a disordered single-band interpretation for the origin of the Kerr effect.
format Preprint
id arxiv_https___arxiv_org_abs_2508_08026
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Terahertz range polarization rotation in the candidate time-reversal symmetry breaking superconductor BiNi
Romero III, Ralph
Tagay, Zhenisbek
Liang, Jiahao
Yan, Jason Y.
Yue, Di
Armitage, N. P.
Superconductivity
Strongly Correlated Electrons
Here we report the observation of time-reversal symmetry (TRS) breaking superconductivity in a BiNi bilayer using terahertz (THz) polarimetry. Leveraging a novel high-precision THz polarimetry technique, we detect, in the superconducting state and at zero magnetic field, the smallest polarization rotation of THz light measured to date. By using the MgO substrate itself as an optical resonator, we can reference the Faraday and Kerr rotations to each other. We observe a low-frequency Kerr rotation on the order of several hundred microradians in the superconducting phase, a clear signature consistent with TRS-breaking superconductivity. Our measurements enable direct access to the THz-range Hall conductivity. Through a Kramers-Kronig analysis, we link these low-energy measurements to prior high-frequency magneto-optic Kerr effect (MOKE) data. This connection provides critical insight into the nature of the TRS-breaking state, supporting a multiband superconducting scenario over a disordered single-band interpretation for the origin of the Kerr effect.
title Terahertz range polarization rotation in the candidate time-reversal symmetry breaking superconductor BiNi
topic Superconductivity
Strongly Correlated Electrons
url https://arxiv.org/abs/2508.08026