Surface Josephson plasma waves in a high-temperature superconductor

Abstract

Electron density oscillations with acoustic dispersions and sustained at boundaries between different media provide information about surface and interface properties of hetero-structures. In ultra-thin metallic films these plasmonic excitations are heavily damped. Superconductivity is predicted to reduce dissipation allowing detection of these resonances. Emerging low-loss interface Cooper-pair waves have been studied before, however, the observation of surface-confined Josephson plasmons has remained elusive. Here, we report on generation and coupling to these excitations in an ultrathin single-crystal film of high-temperature superconductor La1.85Sr0.15CuO4. The film becomes brighter than Au below the critical temperature when probed with sub-gap THz photons. We show that the enhanced signal in the superconducting state, which can be visualized with a spatial resolution better than λ/3,000, originates from near-field coupling of light to surface Josephson plasmons. Our results open a path towards non-invasive investigation of enhanced superconductivity in artificial multilayers, buried interface states in topological hetero-structures, and non-linear phenomena in Josephson devices.

arXiv commentreferences added; expanded discussion; journal reference

References in corpus (18)

• High-temperature interface superconductivity between metallic and insulating cuprates
• Amplitude / Higgs Modes in Condensed Matter Physics
• Persistence of magnetic excitations in La2-xSrxCuO4 from the undoped insulator to the heavily overdoped non-superconducting metal
• Losses in plasmonics: from mitigating energy dissipation to embracing loss-enabled functionalities
• Temporal correlations of superconductivity above the transition temperature in La${}_{2-x}$Sr${}_x$CuO${}_4$ probed by terahertz spectroscopy
• Model for quantitative tip-enhanced spectroscopy and the extraction of nanoscale-resolved optical constants
• Terahertz Josephson plasma waves in layered superconductors: spectrum, generation, nonlinear, and quantum phenomena
• Collective modes and terahertz near-field response of superconductors
• Superconducting plasmonics and extraordinary transmission
• Electron pairing in the pseudogap state revealed by shot noise in copper-oxide junctions
• Generalized spectral method for near-field optical microscopy
• Anomalous Acoustic Plasmon Mode from Topologically Protected States
• Magnetic order in lightly doped La_{2-x}Sr_{x}CuO_{4}
• Infrared nano-spectroscopy and imaging of collective superfluid excitations in conventional and high-temperature superconductors
• In-plane optical conductivity of La${}_{2-x}$Sr${}_x$CuO${}_4$: Reduced superconducting condensate and residual Drude-like response
• Electronic structure of full-shell InAs/Al hybrid semiconductor-superconductor nanowires: Spin-orbit coupling and topological phase space
• Plasmon-polaron of the topological metallic surface states
• Optical Nanoscopy of High-Tc Cuprate Nano-Constriction Devices Patterned by Helium Ion Beams

Cited by in corpus (6)

• Cavity magnon-polaritons in cuprate parent compounds
• Generalized plasma waves in layered superconductors
• Squeezed Josephson plasmons in driven YBa${}_2$Cu${}_3$O${}_{6+x}$
• Theory for Anomalous Terahertz Emission in Striped Cuprate Superconductors
• Optical absorption in tilted geometries as an indirect measurement of longitudinal plasma waves in layered cuprates
• Hybrid collective excitations in topological superconductor/ferromagnetic insulator heterostructures