Reviews in Physics最新文献

Scalar, vector and tensor conserved quantities are essential tools in solving different problems in physics and complex, nonlinear differential equations in mathematics. In many guises they enter our understanding of nature: charge, lepton, baryon numbers conservation accompanied with constant energy, linear or angular total momenta and the conservation of energy–momentum/angular momentum tensors in field theories due to Noether theorem which is based on the translational and Lorentz symmetry of the Lagrangians. One of the oldest discovered conserved quantities is the Laplace–Runge–Lenz vector for the $1/r$-potential. Its different aspects have been discussed many times in the literature. But explicit generalizations to other spherically symmetric potentials are still rare. Here, we attempt to fill this gap by constructing explicit examples of a conserved vector perpendicular to the angular momentum for a class of phenomenologically relevant potentials. Hereby, we maintain the nomenclature and keep calling these constant vectors Laplace–Runge–Lenz vectors.

Topological photonics has attracted increasing attention in recent years due to the unique opportunities it provides to manipulate light in a robust way immune to disorder and defects. Up to now, diverse photonic platforms, rich physical mechanisms and fruitful device applications have been proposed for topological photonics, including one-way waveguide, topological lasing, topological nanocavity, Dirac and Weyl points, Fermi arcs, nodal lines, etc. In this review, we provide an introduction to the field of topological photonics through the lens of topological invariants and bulk-boundary correspondence in one, two, and three dimensions, which may not only offer a unified understanding about the underlying robustness of diverse and distinct topological phenomena of light, but could also inspire further developments by introducing new topological invariants and unconventional bulk-boundary correspondence to the research of topological photonics.

The successful preparation of heterostructures provides more possibilities for the application of mechanics, optoelectronics, and thermoelectronics. Controlling the interlayer interaction of heterostructures can further optimize their performance, hence, it is very important to investigate the interlayer interaction property of heterostructures. Firstly, the crystal structure, energy band structure, exciton behavior, and lattice vibrational of transition metal dichalcogenides (TMDs) are reviewed in this paper. Secondly, the types and interactions of heterostructures are analyzed, such as charge transfer, energy transfer, interlayer exciton, etc. Finally, the factors affecting the interlayer interaction are introduced, which promote the development and application of new devices based on two-dimensional heterostructures in the future.

The paper presents a description of the sound wave absorption in glasses, from the lowest temperatures up to the glass transition, in terms of three compatible phenomenological models. Resonant tunneling, the rise of the relaxational tunneling to the tunneling plateau and the crossover to classical relaxation are universal features of glasses and are well described by the tunneling model and its extension to include soft vibrations and low barrier relaxations, the soft potential model. Its further extension to non-universal features at higher temperatures is the very flexible Gilroy–Phillips model, which allows to determine the barrier density of the energy landscape of the specific glass from the frequency and temperature dependence of the sound wave absorption in the classical relaxation domain. To apply it properly at elevated temperatures, one needs its formulation in terms of the shear compliance. As one approaches the glass transition, universality sets in again with an exponential rise of the barrier density reflecting the frozen fast Kohlrausch $t^{\beta }$-tail (in time $t$, with $\beta$ close to 1/2) of the viscous flow at the glass temperature. The validity of the scheme is checked for literature data of several glasses and polymers with and without secondary relaxation peaks. The frozen Kohlrausch tail of the mechanical relaxation shows no indication of the strongly temperature-dependent barrier density observed in dielectric data of molecular glasses with hydrogen bonds. Instead, the mechanical relaxation data indicate an energy landscape describable with a frozen temperature-independent barrier density for any glass.

Insight into the electroweak (EW) and Higgs sectors can be achieved through measurements of vector boson scattering (VBS) processes. The scattering of EW bosons are rare processes that are precisely predicted in the Standard Model (SM) and are closely related to the Higgs mechanism. Modifications to VBS processes are also predicted in models of physics beyond the SM (BSM), for example through changes to the Higgs boson couplings to gauge bosons and the resonant production of new particles. In this review, experimental results and theoretical developments of VBS at the Large Hadron Collider, its high luminosity upgrade, and future colliders are presented.

As the "fingerprint" spectrum of substances, surface-enhanced Raman scattering (SERS) has extremely high sensitivity. It can detect the molecular traits on the metal surface and reflect the internal structure information of the substance. It is an excellent surface spectroscopy technology. Nevertheless, SERS substrates rely on roughened substrates and nanoparticles of appropriate size, making it hard to use SERS technology to study smooth surface materials or substrates and molecules that do not have SERS active. With the maturity of scanning probe microscopy (SPM) technology, the tip-enhanced Raman spectroscopy (TERS) combining SPM and Raman spectroscopy technology has solved the typical problems in SERS well. Based on the TERS metal tip structure, the spatial detection resolution can be significantly improved, and the research scale can be raised to the single-molecule level. With the rapid development of TERS technology, detection equipment constructed with the help of different types of SPM-TERS systems, metal tip structures, and enhanced modes are used in bioimaging, medical detection, etc. We recognize that it is necessary to provide some new TERS research results. In this review, we initially reviewed the mechanism and structure of TERS. Subsequently, we introduced different novel SPM-TERS systems. Finally, we summarized the research on the tip, gap, and other characteristics of the TERS system and related applications.

A wider scope in topological semimetals accelerates various attractive quantum phenomena for the last two decades. We here report the detailed investigation of magnetic Co₃Sn₂S₂ Weyl semimetal based on the cobalt accompanied kagome lattice for the first time. We emphasize the highly motivated theoretical and experimental analyses in each topological terms of Co₃Sn₂S₂ that led to intensifying emergent topological materials with inherent properties, particularly in the pursuance of magnetic rich quantum anomalous Hall effect. We additionally highlight the Co₃Sn₂S₂ surface band structure, recognized in the diverse fields of study from the perception of topological properties to modern electrochemistry approaches. From materials perspective, this typical kagome Co₃Sn₂S₂ Weyl semimetal alone has extensively covered more enriching nontrivial surface states than topological insulators and nonmagnetic semimetals even in the absence of magnetic field and external strain. Some specific examples include Weyl nodes linked flat band magnetism, a large anomalous Hall effect, anomalous Hall angle, giant magnetooptical effect, and thermomagnetic Nernst effect. In addition, we selectively extend the review on the undisputed surface band characteristics of Co₃Sn₂S₂, by which a major concept of magnetic Weyl semimetal could hierarchically meet the contemporary quantum phenomena. This strongly led to more focus on nontrivial magnetic topological studies for gaining insightful perspectives.

Since 2003, a new family of states without a clear theoretical interpretation has been measured in the heavy quarkonium spectrum, the so-called $XYZ$ states. While the nature of these states is so far unclear, the experimental search is one of the most active fields in the intensity frontier. In this review, the most important and representative results obtained in this field in recent years are going to be illustrated, providing insights into the nature of these exotic states. The focus will be on the experimental side, describing how it is possible to investigate their exotic nature with respect to the conventional quarkonium states.