arXiv subjects

Jacob Pettine

Publications and source records attributed to Jacob Pettine.

5 recordsLinked to original sources

arXiv2025

Visualizing a Terahertz Superfluid Plasmon in a Two-Dimensional Superconductor

The superconducting gap defines the fundamental energy scale for the emergence of dissipationless transport and collective phenomena in a superconductor. In layered high-temperature cuprate superconductors, where the Cooper pairs are confined to weakly coupled two-dimensional copper-oxygen planes, terahertz (THz) spectroscopy at sub-gap millielectronvolt energies has provided crucial insights into the collective superfluid response perpendicular to the superconducting layers. However, within the copper-oxygen planes the collective superfluid response manifests as plasmonic charge oscillations at energies far exceeding the superconducting gap, obscured by strong dissipation. Here, we present spectroscopic evidence of a below-gap, two-dimensional superfluid plasmon in few-layer Bi2Sr2CaCu2O8+x and spatially resolve its deeply sub-diffractive THz electrodynamics. By placing the superconductor in the near-field of a spintronic THz emitter, we reveal this distinct resonance-absent in bulk samples and observed only in the superconducting phase-and determine its plasmonic nature by mapping the geometric anisotropy and dispersion. Crucially, these measurements offer a direct view of the momentum- and frequency dependent superconducting transition in two dimensions. These results establish a new platform for investigating superfluid phenomena at finite momenta and THz frequencies, highlighting the potential to engineer and visualize superconducting devices operating at ultrafast THz rates.

cond-mat.supr-con↗

arXiv2023

Light-Driven Nanoscale Vectorial Currents

Controlled charge flows are fundamental to many areas of science and technology, serving as carriers of energy and information, as probes of material properties and dynamics, and as a means of revealing or even inducing broken symmetries. Emerging methods for light-based current control offer promising routes beyond the speed and adaptability limitations of conventional voltage-driven systems. However, optical generation and manipulation of currents at nanometer spatial scales remains a basic challenge and a crucial step towards scalable optoelectronic systems for microelectronics and information science. Here, we introduce vectorial optoelectronic metasurfaces in which ultrafast light pulses induce local directional charge flows around symmetry-broken plasmonic nanostructures, with tunable responses and arbitrary patterning down to sub-diffractive nanometer scales. Local symmetries and vectorial current distributions are revealed by polarization- and wavelength-sensitive electrical readout and terahertz (THz) emission, while spatially-tailored global currents are demonstrated in the direct generation of elusive broadband THz vector beams. We show that in graphene, a detailed interplay between electrodynamic, thermodynamic, and hydrodynamic degrees of freedom gives rise to rapidly-evolving nanoscale driving forces and charge flows under extreme temporal and spatial confinement. These results set the stage for versatile patterning and optical control over nanoscale currents in materials diagnostics, THz spectroscopies, nano-magnetism, and ultrafast information processing.

cond-mat.mes-hall↗

arXiv2023

Energy-Resolved Femtosecond Hot Electron Dynamics in Single Plasmonic Nanoparticles

Efficient excitation and harvesting of hot carriers from nanoscale metals is central to many emerging photochemical, photovoltaic, and ultrafast optoelectronic applications. Yet direct experimental evidence of the relevant femtosecond dynamics in ubiquitous tens-of-nanometer gold structures remains lacking, despite the rich interplay between interfacial and internal plasmonic fields, excitation distributions, and scattering processes. To explore the effects of nanoscale structure on these dynamics, we employ a new technique for simultaneous time-, angle-, and energy-resolved photoemission spectroscopy of single plasmonic nanoparticles. Photoelectron velocity distributions reveal bulk-like ballistic hot electron transport in nanorod and nanoshell geometries, with no evidence of surface effects. Energy-resolved dynamics observed in the ~1-2 eV range and extrapolated to lower energies via kinetic Boltzmann theory provide the first direct measurements of hot carrier lifetimes within nanoscale gold. Remarkably, we find that particles with dimensions as small as 10 nm serve as exemplary platforms for studying intrinsic metal dynamics.

cond-mat.mes-hall↗

arXiv2020

Self-Adaptive Amplified Spontaneous Emission Suppression with a Photorefractive Two-Beam Coupling Filter

Amplified spontaneous emission is a source of broadband noise that parasitically limits the achievable gain in laser amplifiers. While optical bandpass filtering elements can suppress these broadband noise contributions, such filters are typically designed around specific frequencies or require manual tuning, rendering them less compatible with tunable laser systems. Here, we introduce a nonlinear self-adaptive filter and demonstrate the suppression of amplified spontaneous emission surrounding the lasing mode of a tunable 780 nm external cavity diode laser, using the two-beam coupling interaction in photorefractive BaTiO$_3$. A peak suppression of $-$10 dB is observed $\pm$2.5 nm from the lasing mode, with an overall 50% filter power throughput. The dynamic photorefractive filter is automatically centered on the peak frequency due to the continuous writing and readout of the volume holographic grating and can thereby also automatically adapt to frequency tuning, drift, or mode hopping with an estimated auto-tuning rate of 100 GHz/s under typical conditions. Additionally, we present opportunities for enhancing filter suppression characteristics via the input intensity ratio and tuning the bandwidth via the coupling angle, toward versatile, self-adaptive optical filtering.

physics.optics↗

arXiv2020

Controlling Hot Electron Spatial and Momentum Distributions in Nanoplasmonic Systems: Volume versus Surface Effects

Hot carrier spatial and momentum distributions in nanoplasmonic systems depend sensitively on the optical excitation parameters and nanoscale geometry, which therefore determine the efficiency and functionality of plasmon-enhanced catalysts, photovoltaics, and nanocathodes. A growing appreciation over the past decade for the distinction between volume- and surface-mediated photoexcitation and electron emission from such systems has underscored the need for direct mechanistic insight and quantification of these two processes. Toward this end, we use angle-resolved photoelectron velocity mapping to directly distinguish volume and surface contributions to nanoplasmonic hot electron emission from gold nanorods as a function of aspect ratio, down to the spherical limit. Nanorods excited along their longitudinal surface plasmon axis exhibit surprising transverse photoemission distributions due to the dominant volume excitation mechanisms, as reproduced via ballistic Monte Carlo modelling. We further demonstrate a screening-induced transition from volume (transverse) to surface (longitudinal) photoemission with red detuning of the excitation laser and determine the relative cross-sections of the two mechanisms via combined volume and surface multiphoton photoemission modelling. Based on these results, we are able to identify geometry- and material-specific contributions to the photoemission cross-sections and offer general principles for designing nanoplasmonic systems to control hot electron excitation and emission distributions.

cond-mat.mes-hall↗