Fundamental Physics Research Articles

Investigating peer recognition across an introductory physics sequence: Do first impressions last?

Investigating peer recognition across an introductory physics sequence: Do first impressions last?

Optical trapping-enhanced probes designed by a deep learning approach

Realizing optical trapping enhancement is crucial in biomedicine, fundamental physics, and precision measurement. Taking the metamaterials with artificially engineered permittivity as photonic force probes in optical tweezers will offer unprecedented opportunities for optical trap enhancement. However, it usually involves multi-parameter optimization and requires lengthy calculations; thereby few studies remain despite decades of research on optical tweezers. Here, we introduce a deep learning (DL) model to attack this problem. The DL model can efficiently predict the maximum axial optical stiffness of Si/Si3N4 (SSN) multilayer metamaterial nanoparticles and reduce the design duration by about one order of magnitude. We experimentally demonstrate that the designed SSN nanoparticles show more than twofold and fivefold improvement in the lateral (k x and k y ) and the axial (k z ) optical trap stiffness on the high refractive index amorphous TiO2 microsphere. Incorporating the DL model in optical manipulation systems will expedite the design and optimization processes, providing a means for developing various photonic force probes with specialized functional behaviors.

Floquet engineering of axion and high-Chern number phases in a topological insulator under illumination

Quantum anomalous Hall, high-Chern number, and axion phases in topological insulators are characterized by its Chern invariant C (respectively, C=1, integer C>1, and C=0 with half-quantized Hall conductance of opposite signs on top and bottom surfaces). They are of recent interest because of novel fundamental physics and prospective applications, but identifying and controlling these phases has been challenging in practice. Here we show that these states can be created and switched between in thin films of Bi_22Se_33 by Floquet engineering, using irradiation by circularly polarized light. We present the calculated phase diagrams of encountered topological phases in Bi_22Se_33, as a function of wavelength and amplitude of light, as well as sample thickness, after properly taking into account the penetration depth of light and the variation of the gap in the surface states. These findings open pathways towards energy-efficient optoelectronics, advanced sensing, quantum information processing and metrology.

Whose work matters? A tool for identifying and developing more inclusive physics textbooks

The lack of representational diversity and role models in physics, including in our textbooks and curricular materials, is an oft-cited contributing factor to the continuing dramatic under-representation of women and people of color in physics. In this work, we develop an automated, Python-based tool for identifying the names and demographics of scientists who are mentioned in indices and chapters of physics textbooks, enabling authors, publishers, and users of physics textbooks to rapidly analyze the demographics of these texts. We quantitatively validate the automated tool using standard machine learning metrics, attaining high accuracy, precision, recall, and F1 scores. The tool is then used to demonstrate two of the many potential applications: examining whose work is mentioned in the entire collection of textbooks used in a representative four-year undergraduate physics major curriculum as well as an analysis of the demographics of scientists mentioned in a selection of ten introductory physics textbooks. Both of the sample analyses result in a similar portrait, showing that the undergraduate physics textbooks examined in this work focus overwhelmingly on work attributed to White men of European, British, and North American descent. This work points to an urgent need for the physics education community, including textbook publishers, authors, and adopters, to work together to broaden our portrayals of physics to reflect the vast diversity of scientists, both historically and contemporaneously, who are working in this field.

A Comparative Review of Models for All-Solid-State Li-Ion Batteries

In recent times, there has been significant enthusiasm for the development of all-solid-state Li-ion batteries. This interest stems from a dual focus on safety—addressing concerns related to toxic and flammable organic liquid electrolytes—and the pursuit of high energy density. While liquid electrolyte batteries currently constitute the vast majority of commercial cells, solid electrolyte batteries show great promise. In parallel with experimental research, computational models clarify several fundamental physics that take place throughout battery operations. Giving up on reviewing a broad screening of the existing literature, we set out to select here a few highly relevant models, emphasizing some fundamental conceptual advancements and offering an in-depth and critical insight into the current state of the art. The papers we selected aim at providing the reader with a tangible and quantitative understanding of how all-solid-state Li-ion batteries operate, including the different mechanisms at play and the mathematical tools required to model the pertinent physics and mechanics.

Information-entropy enabled identifying topological photonic phase in real space

The topological photonics plays an important role in the fields of fundamental physics and photonic devices. The traditional method of designing topological system is based on the momentum space, which is not a direct and convenient way to grasp the topological properties, especially for the perturbative structures or coupled systems. Here, we propose an interdisciplinary approach to study the topological systems in real space through combining the information entropy and topological photonics. As a proof of concept, the Kagome model has been analyzed with information entropy. We reveal that the bandgap closing does not correspond to the topological edge state disappearing. This method can be used to identify the topological phase conveniently and directly, even the systems with perturbations or couplings. As a promotional validation, Su–Schrieffer–Heeger model and the valley-Hall photonic crystal have also been studied based on the information entropy method. This work provides a method to study topological photonic phase based on information theory, and brings inspiration to analyze the physical properties by taking advantage of interdisciplinarity.Graphical

Emerging Bio‐relevant Applications of Polymer Mechanochemistry

AbstractPolymer mechanochemistry has rapidly evolved since the mid‐2000s. Recent advancements highlight the development of mechanophore platforms for the controlled release of bioactive payloads and the exploration of biocompatible activation strategies. These platforms, ranging from furan‐maleimide Diels‐Alder adducts to disulfide motifs with β‐carbonate linkages, demonstrate promising prospects in targeted drug delivery. Additionally, supramolecular assemblies and free radical‐generating mechanophores present innovative avenues for potential therapeutic applications. Biocompatible activation methods, notably high‐intensity and/or low‐intensity focused ultrasound, hold potential for in vivo applications. However, challenges persist in comprehending the fundamental physics of ultrasound and its utilization for activation. Future directions emphasize the importance of simplicity in biocompatible platforms and polymer designs, stability under physiological conditions, and precise control of mechanical activation for enhanced biomedical and clinical utility. Despite the aforementioned chemical and technical obstacles, the outlook for polymer mechanochemistry in biomedical and clinical applications remains promising, urging continued exploration and advancement. Key Scientists

Analyzing interviews on computational thinking for introductory physics students: Toward a generalized assessment

Analyzing interviews on computational thinking for introductory physics students: Toward a generalized assessment

Superhard and Superconducting Bilayer Borophene

Two-dimensional superconductors, especially the covalent metals such as borophene, have received significant attention due to their new fundamental physics, as well as potential applications. Furthermore, the bilayer borophene has recently ignited interest due to its high stability and versatile properties. Here, the mechanical and superconducting properties of bilayer-δ6 borophene are explored by means of first-principles computations and anisotropic Migdal–Eliashberg analytics. We find that the coexistence of strong covalent bonds and delocalized metallic bonds endows this structure with remarkable mechanical properties (maximum 2D-Young’s modulus of ~570 N/m) and superconductivity with a critical temperature of ~20 K. Moreover, the superconducting critical temperature of this structure can be further boosted to ~46 K by applied strain, which is the highest value known among all borophenes or two-dimensional elemental materials.

Introducing a Sequence of (Almost) Unlimited, Zero-Penalty, Interview-Like Assessments Into an Introductory Physics Course: Student Responses and Considerations

Introducing a Sequence of (Almost) Unlimited, Zero-Penalty, Interview-Like Assessments Into an Introductory Physics Course: Student Responses and Considerations

Making in‐the‐moment learning visible: A framework to identify and compare various ways of learning through continuity and discourse change

AbstractSmall group interactions and interactions with near‐peer instructors such as learning assistants serve as fertile opportunities for student learning in undergraduate active learning classrooms. To understand what students take away from these interactions, we need to understand how and what they learn during the moment of their interaction. This study builds on practical epistemology analysis to develop a framework to study this in‐the‐moment learning during interactions by operationalizing it through the lens of discourse change and continuity toward three ends. Using video recordings of students and learning assistants interacting in a variety of contexts including remote, in‐person, and hybrid classrooms in introductory chemistry and physics at two universities, we developed an analytical framework that can characterize learning in the moment of interaction, is sensitive to different kinds of learning, and can be used to compare interactions. The framework and its theoretical underpinnings are described in detail. In‐depth examples demonstrate how the framework can be applied to classroom data to identify and differentiate different ways in which in‐the‐moment learning occurs.

Engineering the topological states of Weyl ferromagnetic CoxMnGay films grown by molecular beam epitaxy

Due to its nontrivial topological state, a magnetic Weyl semimetal often exhibits exotic transport properties that are important for both fundamental physics and potential spintronics applications. In this Letter, we investigate the composition dependences of the structural order, magnetism, and transport properties for the epitaxial Heusler alloy CoxMnGay (CMG) topological Weyl semimetal films grown via molecular beam epitaxy. Our results show that the saturated magnetization, anomalous Hall conductivity, and anomalous Hall angle of CMG are influenced by its composition and structural order. Specifically, we observed that the optimized L21–Co2MnGa alloy exhibits a high intrinsic anomalous Hall conductivity of approximately 913 Ω−1 cm−1 at its maximum, which is attributed to the substantial Berry curvature within its electronic band structures. This study provides valuable insights into how to engineer the topological ferromagnetic state of the Weyl semimetals for future applications.

Future Perspectives for Gamma-ray Burst Detection from Space

Since their first discovery in the late 1960s, gamma-ray bursts have attracted an exponentially growing interest from the international community due to their central role in the most highly debated open questions of the modern research of astronomy, astrophysics, cosmology, and fundamental physics. These range from the intimate nuclear composition of high-density material within the core of ultra-dense neuron stars, to stellar evolution via the collapse of massive stars, the production and propagation of gravitational waves, as well as the exploration of the early universe by unveiling the first stars and galaxies (assessing also their evolution and cosmic re-ionization). GRBs in the past ∼50 years have stimulated the development of cutting-edge technological instruments for observations of high-energy celestial sources from space, leading to the launch and successful operations of many different scientific missions (several of them still in data-taking mode currently). In this review, we provide a brief description of the GRB-dedicated missions from space being designed and developed for the future. The list of these projects, not meant to be exhaustive, shall serve as a reference to interested readers to understand what is likely to come next to lead the further development of GRB research and the associated phenomenology.

Abnormal threshold behaviors of photo-pion production off the proton in the GZK region

The cosmic-ray spectrum structures help to study the acceleration and propagation mechanism of ultra-high energy cosmic rays, and these structures were predicted to culminate in a cut-off, named the Greisen–Zatsepin–Kuzmin (GZK) cut-off, near 5×1019eV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$5\ imes 10^{19}~\ extrm{eV}$$\\end{document} as a result of the inelastic interaction of protons with the 2.73K\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$2.73~\ extrm{K}$$\\end{document} black body radiation. The confirmation of the existence of GZK cut-off was tortuous, leading to activities to explore new physics, such as the cosmic-ray new components, unidentified cosmic-ray origins, unknown propagation mechanism and the modification of fundamental physics concepts like the tiny Lorentz invariance violation (LV). The confirmation of the GZK cut-off provides an opportunity to constrain the LV effect. We use a phenomenological framework to restudy the GZK mechanism under the Planck scale deformation of the proton and pion dispersion relations. Restudying the photon induced pion production of the proton p+γ→p+π0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{p}+\\gamma \\rightarrow \ extrm{p}+\\pi ^0$$\\end{document}, we predict abnormal threshold behaviors of this reaction under different LV modifications. Therefore we can study the LV effects not only from the conventional GZK cut-off, but also from potentially threshold anomalies of the pion production process. We divide the LV parameter space into three regions, and analyze the constraints from current observations in each region. The current observations have set strict restrictions on a certain LV region. However, for others LV regions, further experimental observations and theoretical researches are still needed, and we also find survival space for some theoretical explorations that permit specific LV effects.

What topics of peer interactions correlate with student performance in physics courses?

Research suggests that interacting with more peers about physics course material is correlated with higher student performance. Some studies, however, have demonstrated that different topics of peer interactions may correlate with their performance in different ways, or possibly not at all. In this study, we probe both the peers with whom students interact about their physics course and the particular aspects of the course material about which they interacted in six different introductory physics courses: four lecture courses and two lab courses. Drawing on social network analysis methods, we replicate prior work demonstrating that, on average, students who interact with more peers in their physics courses have higher final course grades. Expanding on this result, we find that students discuss a wide range of aspects of course material with their peers: concepts, small-group work, assessments, lecture, and homework. We observe that in the lecture courses, interacting with peers about concepts is most strongly correlated with final course grade, with smaller correlations also arising for small-group work and homework. In the lab courses, on the other hand, small-group work is the only interaction topic that significantly correlates with final course grade. We use these findings to discuss how course structures (e.g. grading schemes and weekly course schedules) may shape student interactions and add nuance to prior work by identifying how specific types of student interactions are associated (or not) with performance.

Analytical solution to second-harmonic generation of ultrashort laser pulse

We present an analytical method to evaluate the second-harmonic generation (SHG) process of ultrashort laser pulses in a nonlinear medium within the small-signal regime. Building upon the broadband nonlinear coupled wave theory, we derive an analytical solution that allows one to investigate the fundamental physics and detailed dynamics of the nonlinear interaction between ultrashort laser pulses. We find that SHG for ultrashort laser pulses in a nonlinear crystal arises from a series of self-SHG and self sum-frequency generation processes involving different frequency components. We have applied the analytical method to investigate specific pulse profiles with Gaussian and sech functions and found good agreement between analytical theory and numerical simulations, validating the accuracy of the analytical approach. The analytical method enables one to explore the evolution of the second-harmonic wave under various pulse profiles, pulse widths, and crystal thicknesses, and offers a more efficient and insightful approach to study the nonlinear optical dynamics of ultrashort laser pulses.

Fundamental physics studies in time domain and multi-messenger astronomy

The era of ime domain and multi-messenger astronomy is not only leading to the development of a much broader set of detectors and instruments for astrophysical observations, but is also providing the means for astronomy to tie directly to cutting-edge studies in physics. In this manner, fundamental physics (theory and experiment) coupled with a strong theoretical understanding of astrophysical phenomena (guided by high-performance computing simulations) can tie directly to the amazing new observations in astronomy. This paper discusses how physics, astrophysical models, and observations can not only help astronomy probe fundamental physics but guide the needs for next-generation astrophysical missions.

Tunable on-chip optical traps for levitating particles based on single-layer metasurface

Abstract Optically levitated multiple nanoparticles have emerged as a platform for studying complex fundamental physics such as non-equilibrium phenomena, quantum entanglement, and light–matter interaction, which could be applied for sensing weak forces and torques with high sensitivity and accuracy. An optical trapping landscape of increased complexity is needed to engineer the interaction between levitated particles beyond the single harmonic trap. However, existing platforms based on spatial light modulators for studying interactions between levitated particles suffered from low efficiency, instability at focal points, the complexity of optical systems, and the scalability for sensing applications. Here, we experimentally demonstrated that a metasurface which forms two diffraction-limited focal points with a high numerical aperture (∼0.9) and high efficiency (31 %) can generate tunable optical potential wells without any intensity fluctuations. A bistable potential and double potential wells were observed in the experiment by varying the focal points’ distance, and two nanoparticles were levitated in double potential wells for hours, which could be used for investigating the levitated particles’ nonlinear dynamics, thermal dynamics and optical binding. This would pave the way for scaling the number of levitated optomechanical devices or realizing paralleled levitated sensors.

NOON-state interference in the frequency domain

The examination of entanglement across various degrees of freedom has been pivotal in augmenting our understanding of fundamental physics, extending to high dimensional quantum states, and promising the scalability of quantum technologies. In this paper, we demonstrate the photon number path entanglement in the frequency domain by implementing a frequency beam splitter that converts the single-photon frequency to another with 50% probability using Bragg scattering four-wave mixing. The two-photon NOON state in a single-mode fiber is generated in the frequency domain, manifesting the two-photon interference with two-fold enhanced resolution compared to that of single-photon interference, showing the outstanding stability of the interferometer. This successful translation of quantum states in the frequency domain will pave the way toward the discovery of fascinating quantum phenomena and scalable quantum information processing.

Graphene-based spintronics

Graphene, the first isolated two-dimensional atomic crystal, is about to pass its 20th year. The last decade has been a critical period for graphene to gradually move from the laboratory to practical applications, and the research on the spin-related physical properties and various spintronic applications of graphene is still enduring. In this review, we systematically retrospect the important and state-of-art progresses about graphene-based spintronics. First, spin–orbit coupling and various tuning means in graphene have been introduced, such as adatoms, electrical control, and the proximity effect. Second, several methods for inducing magnetism in graphene are summarized, including defect, atom doping, proximity effect, and the recently attractive twisted magic-angle. Third, graphene-based lateral and vertical spin valves are discussed, along with some emergent spin transport properties, including spin injection, scattering, and relaxation. Fourth, graphene-based spin logic circuits for spin communications and multifunctional spin logic devices are exhibited. Finally, some significant opportunities and challenges of graphene-based spintronics for the fundamental physics and practical applications in the future are briefly discussed.