A5103149240- Laser-Matter Interactions and Applications
- Advanced Chemical Physics Studies
- Magnetic properties of thin films
- Organic and Molecular Conductors Research
- Electron and X-Ray Spectroscopy Techniques
- Mass Spectrometry Techniques and Applications
- Spectroscopy and Quantum Chemical Studies
- Magnetic Properties and Applications
- Quantum and electron transport phenomena
- Transition Metal Oxide Nanomaterials
- Electronic and Structural Properties of Oxides
- Inorganic Chemistry and Materials
- Advanced Materials Characterization Techniques
- Magneto-Optical Properties and Applications
- Laser-induced spectroscopy and plasma
- Advanced Fiber Laser Technologies
- Advanced Electron Microscopy Techniques and Applications
- Ga2O3 and related materials
- Advanced X-ray Imaging Techniques
- Solid-state spectroscopy and crystallography
- 2D Materials and Applications
- Machine Learning in Materials Science
- Microstructure and Mechanical Properties of Steels
- Semiconductor Quantum Structures and Devices
- Advanced Condensed Matter Physics
Joint Institute for Laboratory Astrophysics
2016-2020
State Key Laboratory of Surface Physics
2020
Fudan University
2008-2020
National Institute of Standards and Technology
2017-2020
University of Colorado Boulder
2016-2019
University of Colorado System
2019
Michigan State University
2012-2016
Attosecond spectroscopic techniques have made it possible to measure differences in transport times for photoelectrons from localized core levels and delocalized valence bands solids. We report the application of attosecond pulse trains directly unambiguously difference lifetimes between born into free electron-like states those excited unoccupied band structure nickel (111). An enormous increase lifetime 212 ± 30 attoseconds occurs when final state coincides with a short-lived state....
Using optical, TEM, and ultrafast electron diffraction experiments we find that single crystal ${\mathrm{VO}}_{2}$ microbeams gently placed on insulating substrates or metal grids exhibit different behaviors, with structural metal-insulator transitions occurring at the same temperature for substrates, while a new monoclinic phase lies between metallic rutile phase. The electronic in these are strongly first order discuss their origins context of current understanding multiorbital splitting,...
High-harmonic spectroscopies reveal that fast energy transfer within 20 fs triggers ultrafast magnetic phase transition in Ni.
Circularly polarized attosecond pulse trains in the EUV region were reconstructed using 3D metrology.
The excitation of a ferromagnetic film by femtosecond laser pulse causes an unexpectedly fast quenching the film's magnetization on subpicosecond time scales. microscopic physical mechanisms responsible for this remain scientific puzzle. authors employ extreme ultraviolet pulses produced high harmonic generation to follow how thin cobalt evolves after 40-fs pulse. By measuring time-, energy-, and angle-resolved magneto-optical response Co films across ${M}_{2,3}$ absorption edge, they obtain...
Significance Electron–electron interactions are among the fastest processes in materials that determine their fascinating properties, occurring on attosecond timescales up (1 as = 10 −18 s). The recent development of angle-resolved photoemission spectroscopy (atto-ARPES) using high harmonic generation has opened possibility probing electron–electron real time. In this paper, we distinguish screening and charge scattering time domain individual energy bands within a solid. These results open...
By correlating time- and angle-resolved photoemission time-resolved transverse magneto-optical Kerr effect measurements, both at extreme ultraviolet wavelengths, we uncover the universal nature of ultrafast photoinduced magnetic phase transition in Ni. This allows us to explain response Ni all laser fluences-from a small reduction magnetization low fluences, complete quenching high fluences. Both probe methods exhibit same demagnetization recovery timescales. The spin system absorbs energy...
Ultrafast laser pulses uncover a new metastable state in 1 T -TaSe 2 by exciting electrons and then tracking their temperature.
Abstract Photoinduced threshold switching processes that lead to bistability and the formation of metastable phases in photoinduced phase transition VO 2 are elucidated through ultrafast electron diffraction diffusive scattering techniques with varying excitation wavelengths. We uncover two distinct regimes dynamical change: a nearly instantaneous crossover into an intermediate state its decay led by lattice instabilities over 10 ps timescales. The structure this is identified be monoclinic,...
Ultrashort light pulses can selectively excite charges, spins, and phonons in materials, providing a powerful approach for manipulating their properties. Here we use femtosecond laser to coherently manipulate the electron phonon distributions, couplings, charge-density wave (CDW) material 1T-TaSe2 After exciting with pulse, fast spatial smearing of laser-excited electrons launches coherent lattice breathing mode, which turn modulates temperature. This finding is contrast all previous...
Optical solitons in multimode nonlinear optical systems offer a unique platform for exploring the interplay of nonlinearity, dispersion, and spatial mode coupling, offering insights into complex wave phenomena. Multi-pass cavities (MPCs) incorporating Kerr media serve as prototypical systems, enabling high-efficiency supercontinuum generation pulse compression. However, stabilizing femtosecond laser pulses solid-medium-based MPCs (solid MPCs) under high nonlinearity remains significant...
In this paper, we review the development and application of coherent short wavelength light sources implemented using high harmonic generation (HHG) process. The physics underlying HHG brought quantum into domain attosecond time-scales for first time. observation manipulation electron dynamics on such time-scales—a capability not conceived—of just a few decades ago—is becoming both more-and-more sophisticated useful as route to achieve exquisite control over light. New experimental...
The electron-phonon mechanism that gives rise to various charge-ordered systems is often controversial because of the cooperative nature transformation, and structural aspect transformation generally poorly understood. Using femtosecond electron crystallography, we reveal a two-step ($\ensuremath{\approx}$400 fs 3.3 ps) suppression order parameter two-dimensional charge-density wave (CDW) clearly decouples from its electronic counterpart following optical quenching. Through atomic...
A frontier challenge in implementing femtosecond electron microscopy is to gain precise optical control of intense beams mitigate collective space charge effects for significantly improving the throughput. Here, we explore flexible uses an RF cavity as a longitudinal lens high-intensity beam column condensing both temporally and spectrally, relevant design ultrafast microscopy. Through introduction novel atomic grating approach characterization bunch phase optics, elucidate principles...
In low-dimensional electronic materials, the charge or spin ordering can be subtly controlled by specific mode modes, giving rise to functioning states such as charge- and spin-density waves, Mott insulators, superconductors. The coupling between electrons atomic lattice effectively investigated ultrafast optical, photoemission, electron diffraction techniques providing detailed description of microscopic collective state evolutions in separate subsystems. However, phononic relaxation time...
Attosecond pulses and pulse trains generated by high-order harmonic generation are finding broad applications in advanced spectroscopies imaging, enabling sub-femtosecond electron dynamics to be probed atomic, molecular material systems.To date, isolated attosecond have been either using very short few-cycle driving pulses, or temporal polarization gating, taking advantage of phase-matching gating.Here we show that high harmonics with a two-color linearly polarized laser field, the window...
Using laser-dressed photoelectron spectroscopy from solids, we completely characterized the circularly polarized harmonics and reconstructed complex 3D waveform of attosecond pulse train.
Using tabletop high harmonics to probe laser-driven demagnetization dynamics, we uncover the role of ultrafast magnon excitations, enhanced electron temperature and transient reduction exchange splitting.
We use attosecond pulse trains to directly measure photoelectron lifetimes in Ni(111) and Cu(111). observe a strong influence of material band structure on the measured lifetimes, which reveal timescale electron screening scattering.
Using laser-dressed photoelectron spectroscopy from solids, we fully characterize circularly polarized harmonics for the first time to reconstruct complex 3D waveform of a attosecond pulse train.
Using laser-dressed photoelectron spectroscopy from solids, we completely characterized the circularly polarized harmonics and reconstructed complex 3D waveform of attosecond pulse train.
We use attosecond pulse trains to directly measure photoelectron lifetimes in Ni(111) and Cu(111). observe a strong influence of material band structure on the measured lifetimes, which reveal timescale electron screening scattering.