A5006809268- 2D Materials and Applications
- Semiconductor Quantum Structures and Devices
- Chalcogenide Semiconductor Thin Films
- Perovskite Materials and Applications
- Graphene research and applications
- Quantum and electron transport phenomena
- Molecular Junctions and Nanostructures
- Mechanical and Optical Resonators
- Photonic and Optical Devices
- Topological Materials and Phenomena
- Advanced Chemical Physics Studies
- MXene and MAX Phase Materials
- Spectroscopy and Laser Applications
- Advanced Semiconductor Detectors and Materials
- Nuclear Physics and Applications
- Inorganic Fluorides and Related Compounds
- Electronic and Structural Properties of Oxides
- Atmospheric Ozone and Climate
- Advanced Memory and Neural Computing
- Phase-change materials and chalcogenides
- Physics of Superconductivity and Magnetism
Center for Integrated Nanotechnologies
2022-2024
Los Alamos National Laboratory
2022-2024
University of California, Irvine
2022-2023
The University of Texas at Austin
2019-2021
University of Würzburg
2017
La Trobe University
1979-1982
Resolving the momentum degree of freedom excitons - electron-hole pairs bound by Coulomb attraction in a photoexcited semiconductor, has remained largely elusive goal for decades. In atomically thin semiconductors, such capability could probe forbidden dark excitons, which critically impact proposed opto-electronic technologies, but are not directly accessible via optical techniques. Here, we momentum-state WSe2 monolayer photoemitting their constituent electrons, and resolving them time,...
We visualize the distribution of electron around hole in an exciton and observe its elusive anomalous dispersion.
Excitons, bound electron–hole pairs in a 2D plane, dominate the optical properties of monolayer transition metal dichalcogenides (TMDs). A large exciton binding energy on order 0.5 eV was theoretically predicted and experimentally determined recently. These ultrastable excitons thus open an avenue to explore physics such as Bose–Einstein condensation superfluidity at room temperature (Kasprzak et al 2006 Nature 443 409; Plumhof 2014 Nat. Mater. 13 247; Fogler Commun. 5 4555; Jiang John Sci....
Physical states in nanoscale solids are tied to their crystalline order, morphology, and size. However, deterministically accessing different nanocrystal morphologies from a single phase usually involves complex synthetic routes, catalysts, or multi-step lithographic techniques. Here, we demonstrate the catalyst-free synthesis of nanosheets nanowires based on luminescent 2D van der Waals (vdW) phase, GaTe, as model that manifests atomic precision highly anisotropic quasi-1D substructure. We...
We studied charge carrier recombination in methylammonium lead iodide (MAPbI3) perovskite and the impact of interfaces on lifetime using time-resolved photoluminescence. Pristine films those covered with organic electron hole transport materials (ETM HTM) were investigated at various laser repetition rates ranging from 10 kHz to MHz order separate bulk interface-affected recombination. revealed two different components PL decay. The fast component (shorter than 300 ns) is assigned...
A photoelectron study is presented for the outermost bands of molecular solid phase of: NH3, H2O, CO2, SO2 and N2O4. Both gaseous spectra were acquired with 40.81 eV ultraviolet spectroscopy (UPS) techniques (except N2O4). For solids, charging effects measured systematically appropriate corrections made. Some valence band shifts observed, as well significant changes in widths, between gas spectra, but general much less than those by previous workers. These results are interpreted terms...
Confining materials to two-dimensional forms changes the behavior of electrons and enables new devices. However, most are challenging produce as uniform thin crystals. Here, we present a synthesis approach where crystals grown in nanoscale mold defined by atomically-flat van der Waals (vdW) materials. By heating compressing bismuth vdW made hexagonal boron nitride (hBN), grow ultraflat less than 10 nanometers thick. Due quantum confinement, bulk states gapped, isolating intrinsic Rashba...
Composite quasi-particles with emergent functionalities in spintronic and quantum information science can be realized correlated materials due to entangled charge, spin, orbital, lattice degrees of freedom. Here we show that by reducing the lateral dimension antiferromagnet NiPS
We use a table-top time-resolved ARPES based on MHz XUV source to directly observe direct and momentum-forbidden excitons in the full first Brillouin zone of WSe 2 monolayer measure their ultrafast dynamics.
Abstract Composite quasi-particles with emergent functionalities in spintronic and quantum information science can be realized correlated materials due to entangled charge, spin, orbital, lattice degrees of freedom. 1-3 Here we show that by reducing the lateral dimension antiferromagnet NiPS 3 flakes tens nanometers, switch-off bulk spin-orbit exciton near-infrared (1.47 eV) 4-6 activate visible-range (1.8 – 2.2 transitions charge-transfer character. These ultra-sharp lines (<120 meV at...
We use a table-top time-resolved ARPES based on MHz XUV source to directly observe direct and momentum-forbidden excitons in the full first Brillouin zone of WSe 2 monolayer measure their ultrafast dynamics.
An exciton, a two-body composite quasiparticle formed of an electron and hole, is fundamental optical excitation in condensed-matter systems. Since its discovery nearly century ago, measurement the excitonic wavefunction has remained beyond experimental reach. Here, we directly image reciprocal space by measuring momentum distribution electrons photoemitted from excitons monolayer WSe2. By transforming to real space, obtain visual around hole exciton. Further, also resolving energy...
Using time- and angle-resolved photoemission spectroscopy on a microscopic sample of 2D semiconductor, we visualized directly the excitonic wavefunction in real- momentum-space.