A5048622785- Plasmonic and Surface Plasmon Research
- Strong Light-Matter Interactions
- 2D Materials and Applications
- Mechanical and Optical Resonators
- Gold and Silver Nanoparticles Synthesis and Applications
- Molecular Junctions and Nanostructures
- Nanowire Synthesis and Applications
- Radiation Detection and Scintillator Technologies
- Graphene research and applications
- Advanced Semiconductor Detectors and Materials
- Topological Materials and Phenomena
- Thermal Radiation and Cooling Technologies
- Quantum and electron transport phenomena
- Surface and Thin Film Phenomena
- Transition Metal Oxide Nanomaterials
- Nonlinear Optical Materials Studies
- Ga2O3 and related materials
- Photoacoustic and Ultrasonic Imaging
- Quantum Dots Synthesis And Properties
- Photonic Crystals and Applications
- Terahertz technology and applications
- Copper-based nanomaterials and applications
- Photonic and Optical Devices
- Gas Sensing Nanomaterials and Sensors
- Boron and Carbon Nanomaterials Research
Columbia University
2020-2025
Stanford University
2017-2025
Radboud University Nijmegen
2023
National Renewable Energy Laboratory
2023
Tsinghua University
2023
University of Washington
2023
The London College
2023
CapeSym (United States)
2018
Nanoscale charge control is a key enabling technology in plasmonics, electronic band structure engineering, and the topology of two-dimensional materials. By exploiting large electron affinity α-RuCl3, we are able to visualize quantify massive transfer at graphene/α-RuCl3 interfaces through generation charge-transfer plasmon polaritons (CPPs). We performed nanoimaging experiments on both ambient cryogenic temperatures discovered robust plasmonic features otherwise ungated undoped structures....
Natural hyperbolic materials with dielectric permittivities of opposite signs along different principal axes can confine long-wavelength electromagnetic waves down to the nanoscale, well below diffraction limit. Confined coupled phonons in dielectrics including hexagonal boron nitride (hBN) and α-MoO3 are referred as phonon polaritons (HPPs). HPP dissipation at ambient conditions is substantial, its fundamental limits remain unexplored. Here, we exploit cryogenic nanoinfrared imaging...
Abstract Polaritons in hyperbolic van der Waals materials—where principal axes have permittivities of opposite signs—are light-matter modes with unique properties and promising applications. Isofrequency contours polaritons may undergo topological transitions from open hyperbolas to closed ellipse-like curves, prompting an abrupt change physical properties. Electronically-tunable are especially desirable for future integrated technologies but yet be demonstrated. In this work, we present a...
Abstract Excitons play a dominant role in the optoelectronic properties of atomically thin van der Waals (vdW) semiconductors. These excitons are amenable to on-demand engineering with diverse control knobs, including dielectric screening, interlayer hybridization, and moiré potentials. However, external stimuli frequently yield heterogeneous excitonic responses at nano- meso-scales, making their spatial characterization conventional diffraction-limited optics formidable task. Here, we use...
Abstract Graphene is a privileged 2D platform for hosting confined light-matter excitations known as surface plasmon polaritons (SPPs), it possesses low intrinsic losses and high degree of optical confinement. However, the isotropic nature graphene limits its ability to guide focus SPPs, making less suitable than anisotropic elliptical hyperbolic materials polaritonic lensing canalization. Here, we present graphene/CrSBr an engineered interface that hosts highly SPP propagation across...
Tungsten ditelluride (WTe2) is an atomically layered transition metal dichalcogenide whose physical properties change systematically from monolayer to bilayer and few-layer versions. In this report, we use apertureless scattering-type near-field optical microscopy operating at Terahertz (THz) frequencies cryogenic temperatures study the distinct THz range electromagnetic responses of mono-, bi- trilayer WTe2 in same multi-terraced micro-crystal. nano-images terraces uncovered weakly...
The ability to create nanometer-scale lateral p-n junctions is essential for the next generation of two-dimensional (2D) devices. Using charge-transfer heterostructure graphene/α-RuCl3, we realize nanoscale in vicinity graphene nanobubbles. Our multipronged experimental approach incorporates scanning tunneling microscopy (STM) and spectroscopy (STS) scattering-type near-field optical (s-SNOM) simultaneously probe electronic responses nanobubble junctions. STM/STS results reveal that with a...
Abstract Exciton polaritons are quasiparticles of photons coupled strongly to bound electron-hole pairs, manifesting as an anti-crossing light dispersion near exciton resonance. Highly anisotropic semiconductors with opposite-signed permittivities along different crystal axes predicted host exotic modes inside the called hyperbolic (HEPs), which confine subdiffractionally enhanced density states. Here, we show observational evidence steady-state HEPs in van der Waals magnet chromium sulfide...
Pump-probe nano-optical experiments were used to study the light-induced insulator metal transition (IMT) in thin films of vanadium dioxide (${\mathrm{VO}}_{2}$), a prototypical correlated electron system. We show that inhomogeneous optical contrast is prompted by spatially uniform photoexcitation, indicating an photosusceptibility ${\mathrm{VO}}_{2}$. locally characterize temperature and time dependent variations photoexcitation threshold necessary induce IMT on picosecond timescales with...
Correlated metals may exhibit unusually high resistivity that increases linearly in temperature, breaking through the Mott-Ioffe-Regel bound, above which coherent quasiparticles are destroyed. The fate of collective charge excitations, or plasmons, these systems is a subject debate. Several studies have suggested plasmons overdamped, whereas other detected propagating plasmons. In this work, we present direct nano-optical images low-loss hyperbolic plasmon polaritons (HPPs) correlated van...
We investigate transient nanotextured heterogeneity in vanadium dioxide (VO2) thin films during a light-induced insulator-to-metal transition (IMT). Time-resolved scanning near-field optical microscopy (Tr-SNOM) is used to study VO2 across wide parameter space of infrared frequencies, picosecond time scales, and elevated steady-state temperatures with nanoscale spatial resolution. Room temperature, steady-state, phonon enhanced nano-optical contrast reveals preexisting "hidden" disorder. The...
Anisotropic dielectric tensors of uniaxial van der Waals (vdW) materials are difficult to investigate at infrared frequencies. The small dimensions high-quality exfoliated crystals prevent the use diffraction-limited spectroscopies. Near-field microscopes coupled broadband lasers can function as Fourier transform spectrometers with nanometric spatial resolution (nano-FTIR). Although functions isotropic be readily extracted from nano-FTIR spectra, in- and out-of-plane permittivities...
Significance Nonlinear optics in topological semimetals is a burgeoning field of research with an expanding list new materials but limited choice probes. We devised, modeled, and implemented approach for investigating nonlinear at the nanoscale metallic tip. Far-field are diffraction-limited probe in-plane response only. Our tip-based circumvents diffraction limit provides strong enhancement both out-of-plane fields. therefore gain access to complete tensors including components not...
The integration time and signal-to-noise ratio are inextricably linked when performing scanning probe microscopy based on raster scanning. This often yields a large lower bound the measurement time, for example, in nano-optical imaging experiments performed using near-field optical microscope (SNOM). Here, we utilize sparse augmented with Gaussian process regression to bypass constraint. We apply this approach image charge-transfer polaritons graphene residing ruthenium trichloride (α-RuCl
The use of work-function-mediated charge transfer has recently emerged as a reliable route toward nanoscale electrostatic control individual atomic layers. Using α-RuCl3 2D electron acceptor, we are able to induce emergent nano-optical behavior in hexagonal boron nitride (hBN) that arises due interlayer polarization. scattering-type scanning near-field optical microscopy (s-SNOM), find thin layer adjacent an hBN slab reduces the propagation length phonon polaritons (PhPs) significant excess...
Graphene is a privileged 2D platform for hosting confined light-matter excitations known as surface plasmon-polaritons (SPPs), it possesses low intrinsic losses with high degree of optical confinement. However, the inherently isotropic properties graphene limit its ability to guide and focus SPPs, making less suitable than anisotropic elliptical hyperbolic materials polaritonic lensing canalization. Here, we present graphene/CrSBr heterostructure an engineered interface that hosts highly SPP...
Correlated materials may exhibit unusually high resistivity increasing linearly in temperature, breaking through the Mott-Ioffe-Regel bound, above which coherent quasiparticles are destroyed. The fate of collective charge excitations, or plasmons, these systems is a subject debate. Several studies suggest plasmons overdamped while others detect unrenormalized plasmons. Here, we present direct optical images low-loss hyperbolic plasmon polaritons (HPPs) correlated van der Waals metal MoOCl2....
Abstract Exciton polaritons are quasiparticles of photons coupled strongly to bound electron-hole pairs, manifesting as an anti-crossing light dispersion near exciton resonance. Highly-anisotropic semiconductors with opposite-signed permittivities along different crystal axes predicted host exotic modes called hyperbolic (HEPs), which permit spatial confinement beyond the material cone and enhanced density states. Here, we show first observational evidence steady-state HEPs using a cryogenic...