Javier Aizpurua's research while affiliated with Donostia International Physics Center and other places

Publications (391)

Preprint
The optical resonances supported by nanostructures offer the possibility to enhance the interaction between matter and the quantum states of light. In this work, we provide a framework to study the scattering of quantum states of light with information encoded in their helicity by a nanostructure. We analyze the purity of the scattered output quant...
Preprint
Full-text available
We use a recently derived gauge-invariant formulation of the problem of an incoherently-driven two-level system coupled to an optical cavity, to explore the transition between different coupling regimes -- in particular, between the weak, and the ultra-strong coupling regimes. We explore this transition using the second-order intensity correlation...
Article
Full-text available
Phonon polariton (PhP) nanoresonators can dramatically enhance the coupling of molecular vibrations and infrared light, enabling ultrasensitive spectroscopies and strong coupling with minute amounts of matter. So far, this coupling and the resulting localized hybrid polariton modes have been studied only by far-field spectroscopy, preventing access...
Article
Hybrid photonic-plasmonic cavities can be tailored to display high Q factors and extremely small mode volumes simultaneously, which ultimately results in large values of the Purcell factor, FP. Amongst the different hybrid configurations, those based on a nanoparticle-on-a-mirror plasmonic cavity provide one of the lowest mode volumes, though so fa...
Preprint
In this article, we address the optomechanical effects in surface-enhanced resonant Raman scattering (SERRS) from a single molecule in a nano-particle on mirror (NPoM) nanocavity by developing a quantum master equation theory, which combines macroscopic quantum electrodynamics and electron-vibration interaction within the framework of open quantum...
Conference Paper
Full-text available
The electromagnetic coupling between quantum emitters (QEs) and plasmonic metallic nanoparticles (MNPs) has attracted great interest in the field of nanophotonics due to the ability of MNPs to strongly enhance the absorption and emission rate of QEs located in close proximity. Typically, the electromagnetic QE-MNPs interaction is addressed using th...
Article
Full-text available
ConspectusMolecular vibrations constitute one of the smallest mechanical oscillators available for micro-/nanoengineering. The energy and strength of molecular oscillations depend delicately on the attached specific functional groups as well as on the chemical and physical environments. By exploiting the inelastic interaction of molecules with opti...
Article
Full-text available
We use time-dependent density functional theory (TDDFT) within the jellium model to study the impact of quantum-mechanical effects on the self-interaction Green’s function that governs the electromagnetic interaction between quantum emitters and plasmonic metallic nanoantennas. A semiclassical model based on the Feibelman parameters, which incorpor...
Chapter
Full-text available
We investigate the interplay of shape changes and localized surface plasmons in small metal particles with the potential of a large enhancement of the inelastic signal from the particles’ own vibrations. The framework is a geometrical one where we study the change in geometric factors during the vibrational movement. The resulting cross-section is...
Preprint
Molecular vibrations couple to visible light only weakly, have small mutual interactions, and hence are often ignored for nonlinear optics. Here we show the extreme confinement provided by plasmonic nanocavities can sufficiently enhance optomechanical coupling so that intense laser illumination drastically softens the molecular bonds. This optomech...
Article
Full-text available
Grain boundaries determine physical properties of bulk materials including ductility, diffusivity, and electrical conductivity. However, the role of grain boundaries in nanostructures and nanoparticles is much less understood, despite the wide application of nanoparticles in nanophotonics, nanoelectronics, and heterogeneous catalysis. Here, we inve...
Preprint
Full-text available
Hybrid photonic-plasmonic cavities can be tailored to display high Q-factors and extremely small mode volumes simultaneously, which results in large values of the Purcell factor, FP. Amongst the different hybrid configurations, those based on a nanoparticle-on-a-mirror (NPoM) plasmonic cavity provide one of the lowest mode volumes, though so far th...
Article
Full-text available
The interactions of the excited states of a single chromophore with static and dynamic electric fields spatially varying at the atomic scale are investigated in a joint experimental and theoretical effort. In this configuration, the spatial extension of the fields confined at the apex of a scanning tunneling microscope tip is smaller than that of t...
Conference Paper
We show that the magnetic-modulation of the optical response induced by an external magnetic field in giant-magneto-resistance rod-slit arrays is more sensitive to the presence of a molecular vibration than the direct optical response.
Preprint
Full-text available
Focused beams of electrons, which act as both sources, and sensors of electric fields, can be used to characterise the electric response of complex photonic systems, by locally probing the induced optical near fields. This functionality can be complemented by embracing the recently developed vortex electron beams (VEBs), made up of electrons with o...
Article
Full-text available
Strong coupling between molecular vibrations and microcavity modes has been demonstrated to modify physical and chemical properties of the molecular material. Here, we study the less explored coupling between lattice vibrations (phonons) and microcavity modes. Embedding thin layers of hexagonal boron nitride (hBN) into classical microcavities, we d...
Article
Hybrid photonic-plasmonic cavities have emerged as a new platform to increase light–matter interaction capable to enhance the Purcell factor in a singular way not attainable with either photonic or plasmonic cavities separately. In the hybrid cavities proposed so far, the plasmonic element is usually a metallic bow-tie antenna, so the plasmonic gap...
Article
Full-text available
The ultrafast concentration of electromagnetic energy in nanoscale volumes is one of the key features of optical nanoantennas illuminated at their surface plasmon resonances. Here, we drive the insulator to metal phase transition in vanadium dioxide (VO2) using a laser-induced pumping effect obtained by positioning a single gold nanoantenna in prox...
Preprint
Full-text available
The interactions between the excited states of a single chromophore with static and dynamic electric fields confined to a plasmonic cavity of picometer dimensions are investigated in a joint experimental and theoretical effort. In this configuration, the spatial extensions of the confined fields are smaller than the one of the molecular exciton, a...
Conference Paper
Optical Solar Reflectors (OSRs) play a crucial role in thermal management of spacecraft as the outer-surface to the space environment. To achieve the thermal control, an ideal OSR should be able to reflect all the UV/Vis/NIR spectrum radiation to avoid heating up by the son and also emit blackbody radiation in infrared (IR) spectrum for thermal dis...
Preprint
Full-text available
Hybrid photonic-plasmonic cavities have emerged as a new platform to increase light-matter interaction capable to enhance the Purcell factor in a singular way not attainable with either photonic or plasmonic cavities separately. In the hybrid cavities proposed so far, mainly consisting of metallic bow-tie antennas, the plasmonic gap sizes defined b...
Article
The exact study of small systems can guide us toward relevant measures for extracting information about many-body physics as we move to larger and more complex systems capable of quantum information processing or quantum analog simulation. We use exact diagonalization to study many electrons in short 1-D atom chains represented by long-range extend...
Preprint
Phonon-polaritons, mixed excitations of light coupled to lattice vibrations (phonons), are emerging as a powerful platform for nanophotonic applications. This is because of their ability to concentrate light into extreme sub-wavelength scales and because of their longer phonon lifetimes than their plasmonic counterparts. In this work, the infrared...
Article
Mark Stockman was a founding member and evangelist for the plasmonics field for most of his creative life. He never sought recognition, but fame came to him in a different way. He will be dearly remembered by colleagues and friends as one of the most influential and creative contributors to the science of light from our generation.
Article
Full-text available
Plasmonic cavities can confine electromagnetic radiation to deep sub-wavelength regimes. This facilitates strong coupling phenomena to be observed at the limit of individual quantum emitters. Here, we report an extensive set of measurements of plasmonic cavities hosting one to a few semiconductor quantum dots. Scattering spectra show Rabi splitting...
Article
We present experimental and theoretical results of the molecular sensing performance of a novel platform based on magnetic modulation of surface-enhanced infrared absorption spectroscopy. For this, we study the effect that molecular infrared vibrations of a PMMA layer have on the optical and magneto-refractive response of spintronic antennas. Speci...
Article
Full-text available
Frequency-resolved photon correlations have proven to be a useful resource to unveil nonlinearities hidden in standard observables such as the spectrum or the standard (color-blind) photon correlations. In this manuscript, we analyze the frequency-resolved correlations of the photons being emitted from an optomechanical system where light is nonlin...
Preprint
Full-text available
Strong coupling between molecular vibrations and microcavity modes has been demonstrated to modify physical and chemical properties of the molecular material. Here, we study the much less explored coupling between lattice vibrations (phonons) and microcavity modes. Embedding thin layers of hexagonal boron nitride (hBN) into classical microcavities,...
Article
The surface excitation spectra of the Pd(110) surface is analyzed in the framework of the time-dependent density functional theory. The ab initio electronic structure of this surface is included into the evaluation of the surface response function using a linear response approach. At small momentum transfer the extrapolated energy of the surface pl...
Conference Paper
Metasurface devices are conventionally fabricated by physically patterning the functional film. We demonstrated a novel fabrication technique to selectively modulate Al-doped ZnO carrier concentration of planar film and form a planar optical metasurface.
Article
Phonon‐polaritons, mixed excitations of light coupled to lattice vibrations (phonons), are emerging as a powerful platform for nanophotonic applications. This is because of their ability to concentrate light into extreme sub‐wavelength scales and because of their longer phonon lifetimes compared to their plasmonic counterparts. In this work, the in...
Article
Full-text available
The description of Surface-Enhanced Raman Scattering (SERS) as a molecular optomechanical process has provided new insights into the vibrational dynamics and nonlinearities of this inelastic scattering process. In earlier studies, molecular vibrations have typically been assumed to couple with a single plasmonic mode of a metallic nanostructure, ig...
Article
Increasing the sensitivity of chiral spectroscopic techniques such as circular dichroism (CD) spectroscopy is a current aspiration in the research field of nanophotonics. Enhancing CD spectroscopy depends on two complementary requirements: the enhancement of the electromagnetic fields perceived by the molecules under study and the conservation of t...
Preprint
The exact study of small systems can guide us toward measures for extracting information about many-body physics as we move to more complex systems capable of quantum information processing or quantum analog simulation. We use exact diagonalization to study many electrons in short 1-D atom chains represented by long-range extended Hubbard-like mode...
Article
Full-text available
Ambitions to reach atomic resolution with light have been a major force in shaping nano-optics, whereby a central challenge is achieving highly localized optical fields. A promising approach employs plasmonic nanoantennas, but fluorescence quenching in the vicinity of metallic structures often imposes a strict limit on the attainable spatial resolu...
Article
Complementary metasurfaces composed of randomly-placed arrays of aligned rods or slits are fabricated out of giant magnetoresistance Ni81Fe19/Au multilayers (MLs), a material whose optical properties change under the application of an external static magnetic field. The two metasurfaces are studied from both the experimental and theoretical viewpoi...
Article
Full-text available
We theoretically describe how fast electrons couple to polaritonic modes in uniaxial materials by analyzing the electron energy-loss spectra. We show that in the case of a uniaxial medium with hyperbolic dispersion, bulk and surface modes can be excited by a fast electron traveling through the volume or along an infinite interface between the mater...
Preprint
Full-text available
Frequency-resolved photon correlations have proven to be a useful resource to unveil nonlinearities hidden in standard observables such as the spectrum or the standard (color-blind) photon correlations. In this manuscript, we analyze the frequency-resolved correlations of the photons being emitted from an optomechanical system where light is nonlin...
Article
Full-text available
Tip‐enhanced Raman spectroscopy (TERS) of a single molecule is commonly described by considering the change in the polarizability of the molecule with respect to a normal coordinate induced by homogeneous illumination. However, the local fields induced by nanoscale and atomic‐scale features at the surface of metallic clusters and nanogaps show stro...
Article
Full-text available
In this joint experimental and theoretical study we demonstrate coherent control of the optical field emission and electron transport in plasmonic gaps subjected to intense single-cycle laser pulses. Our results show that an external THz field or a minor dc bias, orders of magnitude smaller than the optical bias owing to the laser field, allows one...
Preprint
Full-text available
We theoretically describe how fast electrons couple to polaritonic modes in uniaxial materials by analyzing the electron energy loss (EEL) spectra. We show that in the case of an uniaxial medium with hyperbolic dispersion, bulk and surface modes can be excited by a fast electron traveling through the volume or along an infinite interface between th...
Article
Full-text available
Argiaren kontzeptuari buruzko perspektiba historiko laburra aurkezten da hemen, bere izaera uhinkorrra azpimarratuz. Izaera uhinkor honek materia eta argiaren arteko elkarrekintzaren zenbait ezaugarri finkatzen ditu, teoria elektromagnetikoaren barruan. Horien artean, aipatzekoa da difrakzio muga, mikrometro erdi baten azpitik argia lokalizatzea ah...
Article
A novel technique for the investigation of the radiative contribution to the electromagnetic local density of states is presented. The inelastic tunneling current from a scanning tunneling microscope (STM) is used to locally and electrically excite the plasmonic modes of a triangular gold platelet. The radiative decay of these modes is detected thr...
Article
The interaction between molecules is commonly ignored in surface-enhanced Raman scattering (SERS). Under this assumption, the total SERS signal is described as the sum of the individual contributions of each molecule treated independently. We adopt here an optomechanical description of SERS within a cavity quantum electrodynamics framework to study...
Preprint
Full-text available
Increasing the sensitivity of chiral spectroscopic techniques such as circular dichroism (CD) spectroscopy is a current aspiration in the research field of nanophotonics. Enhancing CD spectroscopy depends upon of two complementary requirements: the enhancement of the electromagnetic fields perceived by the molecules under study and the conservation...
Article
Full-text available
Tautomerization, the interconversion between two constitutional molecular isomers, is ubiquitous in nature1, plays a major role in chemistry2 and is perceived as an ideal switch function for emerging molecular-scale devices3. Within free-base porphyrin4, porphycene5 or phthalocyanine6, this process involves the concerted or sequential hopping of th...
Article
Full-text available
The strong fields associated with few-cycle pulses can drive highly nonlinear phenomena, allowing the direct control of electrons in condensed matter systems. In this context, by employing near-infrared single-cycle pulse pairs, we measure interferometric autocorrelations of the ultrafast currents induced by optical field emission at the nanogap of...
Article
We use time-dependent density functional theory and a semiclassical model to study second-harmonic generation in a system comprising a quantum emitter and a spherical metallic nanoparticle, where the transition frequency of the quantum emitter is set resonant with the second harmonic of the incident frequency. The quantum emitter is shown to enable...
Article
Full-text available
The dynamic restructuring of metal nanoparticle surfaces is known to greatly influence their catalytic, electronic transport, and chemical binding functionalities. Here we show for the first time that non-equilibrium atomic-scale lattice defects can be detected in nanoparticles by purely optical means. These fluctuating states determine interface e...
Article
The coupling between a molecular emitter and an optical cavity is often addressed theoretically with the molecule regarded as a point dipole, thus lacking any chemical structure. This approximation usually works well because the spatial extent of the electromagnetic fields considered is typically spread over a larger volume than the size of the mol...
Article
Full-text available
The discovery in 1974 of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is considered a landmark in the history of spectroscopic and analytical techniques. Much experimental and theoretical effort has been spent toward understanding the surface enhanced Raman scattering (SERS) effect, and demonstrating it...
Preprint
The interaction between molecules is commonly ignored in surface-enhanced Raman scattering (SERS). Under this assumption, the total SERS signal is described as the sum of the individual contributions of each molecule treated independently. We adopt here an optomechanical description of SERS within a cavity quantum electrodynamics framework to study...
Conference Paper
Optical solar reflectors (OSRs) play a crucial role in the spacecraft thermal management. We present novel OSRs based on planar or non-planar metal oxide metasurface. Fabricated meta-OSRs are shown to give superior emittance performance.
Article
Full-text available
Localised surface plasmons can couple strongly with the electronic transitions of a molecule, inducing new hybridised states of light and matter, the plasmon–exciton polaritons. Furthermore, molecules support vibrational degrees of freedom that interact with the electronic levels, giving rise to inelastic resonant Raman scattering under coherent la...
Article
Full-text available
Improved multiphoton‐excited imaging and microspectroscopy require nanoprobes that can give different nonlinear optical signals. Here, composite nanostructures with a barium titanate core and a plasmonic moiety at their surface are synthesized and characterized. It is found that the core provides a high second‐order nonlinear susceptibility for sen...
Article
Full-text available
Improved multiphoton‐excited imaging and microspectroscopy require nanoprobes that can give different nonlinear optical signals. Here, composite nanostructures with a barium titanate core and a plasmonic moiety at their surface are synthesized and characterized. It is found that the core provides a high second‐order nonlinear susceptibility for sen...
Article
Surface-enhanced Raman scattering (SERS) allows for detection and identification of molecular vibrational fingerprints in minute sample quantities. The SERS process can also be exploited for optical manipulation of molecular vibrations. We present a quantum description of surface-enhanced resonant Raman scattering, in analogy to hybrid cavity optom...
Article
Full-text available
We present magnetic field induced modulation of the optical response of slit plasmonic metasurfaces fabricated out of giant magnetoresistance/spintronic materials in the 2–17 μm spectral range of the spectrum. The modulation of the slit plasmonic modes is due to the modification of the electrical resistivity (and, in turn, of the optical constants)...
Preprint
The strong coupling of quantum emitters to plasmonic cavities has emerged as an exciting frontier in quantum plasmonics and optics. Here we report an extensive set of measurements of plasmonic cavities hosting one to a few semiconductor quantum dots (QDs). Scattering spectra demonstrate that these devices are at or close to the strong coupling regi...
Article
Full-text available
EELS in STEM: the “Swiss Army Knife” of Spectroscopy - Volume 25 Supplement - Juan Carlos Idrobo, Andrea Konečná, Jaume Gazquez, Jordan A. Hachtel, Tracy C. Lovejoy, Niklas Dellby, F. Javier García de Abajo, Mathieu Kociak, Javier Aizpurua, Ondrej L. Krivanek
Preprint
Surface-Enhanced Raman Scattering (SERS) allows for detection and identification of molecular vibrational fingerprints in minute sample quantities. The SERS process can be also exploited for optical manipulation of molecular vibrations. We present a quantum description of Surface-Enhanced Resonant Raman scattering (SERRS), in analogy to hybrid cavi...
Article
Ultrathin dielectric gaps between metals can trap plasmonic optical modes with surprisingly low loss and with volumes below 1 nm ³ . We review the origin and subtle properties of these modes, and show how they can be well accounted for by simple models. Particularly important is the mixing between radiating antennas and confined nanogap modes, whic...
Article
Full-text available
In-Situ Characterization of 2-Dim Materials at High Energy and Spatial Resolution - Volume 25 Issue S1 - Jacob R. Jokisaari, Jordan Hachtel, Xuan Hu, Arijita Mukherjee, Canhui Wang, Andrea Konecna, Javier Aizpurua, Ondrej L. Krivanek, Juan-Carlos Idrobo, Robert F. Klie