Spatiotemporal imaging and shaping of electron wave functions using novel attoclock interferometry.

Electrons detached from atoms by photoionization carry valuable information about light-atom interactions. Characterizing and shaping the electron wave function on its natural timescale is of paramount importance for understanding and controlling ultrafast electron dynamics in atoms, molecules and condensed matter. Here we propose a novel attoclock interferometry to shape and image the electron wave function in atomic photoionization. Using a combination of a strong circularly polarized second harmonic and a weak linearly polarized fundamental field, we spatiotemporally modulate the atomic potential barrier and shape the electron wave functions, which are mapped into a temporal interferometry. By analyzing the two-color phase-resolved and angle-resolved photoelectron interference, we are able to reconstruct the spatiotemporal evolution of the shaping on the amplitude and phase of electron wave function in momentum space within the optical cycle, from which we identify the quantum nature of strong-field ionization and reveal the effect of the spatiotemporal properties of atomic potential on the departing electron. This study provides a new approach for spatiotemporal shaping and imaging of electron wave function in intense light-matter interactions and holds great potential for resolving ultrafast electronic dynamics in molecules, solids, and liquids.

Development of a semi-empirical interatomic potential appropriate for the radiation defects in V-Ti-Ta-Nb high-entropy alloy.

High-entropy alloys (HEAs) hold promise as candidate structural materials in future nuclear energy systems. Body-centred cubic V-Ti-Ta-Nb HEAs have received extensive attention due to their excellent mechanical properties. In this work, the Finnis-Sinclair interatomic potential for quaternary V-Ti-Ta-Nb HEAs has been fitted based on the defect properties obtained with the density functional theory (DFT) calculations. The new potential for Nb accurately reproduces the vacancy formation energy, vacancy migration energy and interstitial formation energy. The typical radiation defect properties predicted by the alloy potential were consistent with the DFT results, including the binding energies between substitutional solute atoms, the binding energy between substitutional atoms and vacancies, and the formation energy of interstitial solute atoms. In addition, the mixing enthalpies of the alloys were also consistent with the DFT results. The present potential can also describe reasonably the collision cascade process of quaternary V-Ti-Ta-Nb HEAs.

Probing the orbital angular momentum of intense vortex pulses with strong-field ionization.

With the rapid development of femtosecond lasers, the generation and application of optical vortices have been extended to the regime of intense-light-matter interaction. The characterization of the orbital angular momentum (OAM) of intense vortex pulses is very critical. Here, we propose and demonstrate a novel photoelectron-based scheme that can in situ distinguish the OAM of the focused intense femtosecond optical vortices without the modification of light helical phase. We employ two-color co-rotating intense circular fields in the strong-field photoionization experiment, in which one color light field is a plane wave serving as the probing pulses and the other one is the vortex pulses whose OAM needs to be characterized. We show that by controlling the spatial profile of the probing pulses, the OAM of the vortex pulses can be clearly identified by measuring the corresponding photoelectron momentum distributions or angle-resolved yields. This work provides a novel in situ detection scenario for the light pulse vorticity and has implications for the studies of ultrafast and intense complex light fields with optical OAM.

Two-dimensional nanosheets of MoS2: a promising material with high dielectric properties and microwave absorption performance.

In this study, few-layered MoS2 nanosheets (MoS2-NS) were obtained via the top-down exfoliation method from bulk MoS2 (MoS2-Bulk), and the dielectric properties and microwave absorption performance of MoS2-NS were first reported. The dimension-dependent dielectric properties and microwave absorption performance of MoS2 were investigated by presenting a comparative study between MoS2-NS and MoS2-Bulk. Our results show that the imaginary permittivity (ε'') of MoS2-NS/wax is twice as large as that of MoS2-Bulk/wax. The minimum reflection loss (RL) value of MoS2-NS/wax with 60 wt% loading is -38.42 dB at a thickness of 2.4 mm, which is almost 4 times higher than that of MoS2-Bulk/wax, and the corresponding bandwidth with effective attenuation (<-10 dB) of MoS2-NS/wax is up to 4.1 GHz (9.6-13.76 GHz). The microwave absorption performance of MoS2-NS is comparable to those reported in carbon-related nanomaterials. The enhanced microwave absorption performance of MoS2-NS is attributed to the defect dipole polarization arising from Mo and S vacancies and its higher specific surface area. These results suggest that MoS2-NS is a promising candidate material not only in fundamental studies but also in practical microwave applications.