Manipulating the symmetry of photon-dressed electronic states.

Strong light-matter interaction provides opportunities for tailoring the physical properties of quantum materials on the ultrafast timescale by forming photon-dressed electronic states, i.e., Floquet-Bloch states.

Association of children's electronic media use with physical activity, cognitive function, and stress.

Objective: Electronic media is constantly evolving and has become an integral part of people's lives, especially among youth. This cross-sectional observational study assessed the association between electronic media use, health behaviors and outcomes, specifically, physical activity, stress and cognitive function among youth from an under-resourced community.

Methods: Participants ages six-sixteen were recruited from a Federally Qualified Health Center to participate in a study to promote park prescriptions with data collection between 2020 and 2024.

Light-Induced Ultrafast Glide-Mirror Symmetry Breaking in Black Phosphorus.

Symmetry breaking plays an important role in the fields of physics, ranging from particle physics to condensed matter physics. In solid-state materials, phase transitions are deeply linked to the underlying symmetry breakings, resulting in a rich variety of emergent phases. Such symmetry breakings are often induced by controlling the chemical composition and temperature or applying an electric field, strain, etc.

Ultrafast Carrier Relaxation Dynamics in a Nodal-Line Semimetal PtSn.

Topological Dirac nodal-line semimetals host topologically nontrivial electronic structure with nodal-line crossings around the Fermi level, which could affect the photocarrier dynamics and lead to novel relaxation mechanisms. Herein, by using time- and angle-resolved photoemission spectroscopy, we reveal the previously inaccessible linear dispersions of the bulk conduction bands above the Fermi level in a Dirac nodal-line semimetal PtSn, as well as the momentum and temporal evolution of the gapless nodal lines. A surprisingly ultrafast relaxation dynamics within a few hundred femtoseconds is revealed for photoexcited carriers in the nodal line.

Association Between Park Use and Moderate-to-Vigorous Activity During COVID-19 Years among a Cohort of Low-Income Youth.

Neighborhood parks are important venues to support moderate-to-vigorous (MVPA) activity. There has been a noticeable increase promoting physical activity among youth in neighborhood parks. This paper aims to assess the association between park use and MVPA among low-income youth in a large urban area.

Floquet Engineering of Black Phosphorus upon Below-Gap Pumping.

Time-periodic light field can dress the electronic states and lead to light-induced emergent properties in quantum materials. While below-gap pumping is regarded favorable for Floquet engineering, so far direct experimental evidence of momentum-resolved band renormalization still remains missing. Here, we report experimental evidence of light-induced band renormalization in black phosphorus by pumping at photon energy of 160 meV, which is far below the band gap, and the distinction between below-gap pumping and near-resonance pumping is revealed.

Pseudospin-selective Floquet band engineering in black phosphorus.

Time-periodic light field has emerged as a control knob for manipulating quantum states in solid-state materials, cold atoms and photonic systems through hybridization with photon-dressed Floquet states in the strong-coupling limit, dubbed Floquet engineering. Such interaction leads to tailored properties of quantum materials, for example, modifications of the topological properties of Dirac materials and modulation of the optical response. Despite extensive research interests over the past decade, there is no experimental evidence of momentum-resolved Floquet band engineering of semiconductors, which is a crucial step to extend Floquet engineering to a wide range of solid-state materials.

A newly designed femtosecond KBeBOF device with pulse duration down to 55 fs for time- and angle-resolved photoemission spectroscopy.

Developing a widely tunable vacuum ultraviolet (VUV) source with a sub-100 fs pulse duration is critical for ultrafast pump-probe techniques such as time- and angle-resolved photoemission spectroscopy (TrARPES). While a tunable probe source with a photon energy of 5.3-7.

Ultrafast time- and angle-resolved photoemission spectroscopy with widely tunable probe photon energy of 5.3-7.0 eV for investigating dynamics of three-dimensional materials.

Time- and angle-resolved photoemission spectroscopy (TrARPES) is a powerful technique for capturing the ultrafast dynamics of charge carriers and revealing photo-induced phase transitions in quantum materials. However, the lack of widely tunable probe photon energy, which is critical for accessing the dispersions at different out-of-plane momentum k in TrARPES measurements, has hindered the ultrafast dynamics investigation of 3D quantum materials, such as Dirac or Weyl semimetals. Here, we report the development of a TrARPES system with a highly tunable probe photon energy from 5.

Population Inversion and Dirac Fermion Cooling in 3D Dirac Semimetal CdAs.

Revealing the ultrafast dynamics of three-dimensional (3D) Dirac fermions is critical for both fundamental science and device applications. So far, how the cooling of 3D Dirac fermions differs from that of two-dimensional (2D) and whether there is population inversion are fundamental questions to be answered. Here we reveal the ultrafast dynamics of Dirac fermions in a model 3D Dirac semimetal CdAs by time- and angle-resolved photoemission spectroscopy with a tunable probe photon energy.

Light-Tunable Surface State and Hybridization Gap in Magnetic Topological Insulator MnBiTe.

MnBiTe is an intrinsic ferromagnetic (FM) topological insulator with different complex surface terminations. Resolving the electronic structures of different termination surfaces and manipulation of the electronic state are important. Here, by using micrometer spot time- and angle-resolved photoemission spectroscopy (μ-TrARPES), we resolve the electronic structures and reveal the ultrafast dynamics upon photoexcitation.

Complete convergence and complete moment convergence for weighted sums of extended negatively dependent random variables under sub-linear expectation.

In this paper, we study the complete convergence and complete moment convergence for weighted sums of extended negatively dependent (END) random variables under sub-linear expectations space with the condition of [Formula: see text], further [Formula: see text], [Formula: see text] ([Formula: see text] is a slow varying and monotone nondecreasing function). As an application, the Baum-Katz type result for weighted sums of extended negatively dependent random variables is established under sub-linear expectations space. The results obtained in the article are the extensions of the complete convergence and complete moment convergence under classical linear expectation space.