Physics

25 pages, 1706 KB

Open AccessArticle

A Comparison of Quantum and Semiclassical Rabi Models Near Multiphoton Resonances in the Presence of Parametric Modulation

by Marcos V. S. de Paula, Marco A. Damasceno Faustino and Alexandre V. Dodonov

Physics 2025, 7(3), 42; https://doi.org/10.3390/physics7030042 - 16 Sep 2025

Abstract

We compare the semiclassical and quantum predictions for the unitary dynamics of a two-level atom interacting with a single-mode electromagnetic field under parametric modulation of the atomic parameters in the regime of multiphoton atom–field resonances. We derive approximate analytic solutions for the semiclassical [...] Read more.

We compare the semiclassical and quantum predictions for the unitary dynamics of a two-level atom interacting with a single-mode electromagnetic field under parametric modulation of the atomic parameters in the regime of multiphoton atom–field resonances. We derive approximate analytic solutions for the semiclassical Rabi model when the atomic transition frequency and the atom–field coupling strength undergo harmonic external modulations. These solutions are compared to the predictions of the quantum Rabi model, which we solve numerically for an initial coherent state with a large average photon number (on the order of

10^{4}

), in the regime of three-photon resonance. We show that, for short enough times and sufficiently intense coherent states, the semiclassical dynamics agrees quite well with the quantum dynamics, although it inevitably fails at longer times due to the absence of collapse–revival behavior. Furthermore, we describe how the field state evolves throughout the interaction, presenting numerical results for the average photon number, entropies (related to atom–field entanglement), and other quantities characterizing the photon number statistics of the electromagnetic field. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor Viktor Dodonov—55 Years in Quantum Physics)

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24 pages, 495 KB

Open AccessReview

Dynamical Transitions in Trapped Superfluids Excited by Alternating Fields

by Vyacheslav I. Yukalov and Elizaveta P. Yukalova

Physics 2025, 7(3), 41; https://doi.org/10.3390/physics7030041 - 12 Sep 2025

Abstract

The paper presents a survey of some dynamical transitions in nonequilibrium trapped Bose-condensed systems subject to the action of alternating fields. Nonequilibrium states of trapped systems can be implemented in two ways: resonant and nonresonant. Under resonant excitation, several coherent modes are generated [...] Read more.

The paper presents a survey of some dynamical transitions in nonequilibrium trapped Bose-condensed systems subject to the action of alternating fields. Nonequilibrium states of trapped systems can be implemented in two ways: resonant and nonresonant. Under resonant excitation, several coherent modes are generated by external alternating fields with the frequencies been tuned to resonance with some transition frequencies of the trapped system. A Bose system of trapped atoms with Bose–Einstein condensate can display two types of the Josephson effect, the standard one, when the system is separated into two or more parts in different locations, or the internal Josephson effect, when there are no any separation barriers but the system becomes nonuniform due to the coexistence of several coherent modes interacting one with another. The mathematics in both these cases is similar. We focus on the internal Josephson effect. Systems with nonlinear coherent modes demonstrate rich dynamics, including Rabi oscillations, the Josephson effect, and chaotic motion. Under the Josephson effect, there exist dynamic transitions that are similar to phase transitions in equilibrium systems. The bosonic Josephson effect is shown to be implementable not only for quite weakly interacting systems, but also in superfluids with not necessarily as weak interactions. Sufficiently strong nonresonant excitation can generate several types of nonequilibrium states comprising vortex germs, vortex rings, vortex lines, vortex turbulence, droplet turbulence, and wave turbulence. Nonequilibrium states are shown to be characterized and distinguished by effective temperature, effective Fresnel number, and dynamic scaling laws. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor Viktor Dodonov—55 Years in Quantum Physics)

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8 pages, 260 KB

Open AccessCommunication

Generation of Zonal Flows in a Rotating Self-Gravitating Fluid

by Volodymyr M. Lashkin and Oleg K. Cheremnykh

Physics 2025, 7(3), 40; https://doi.org/10.3390/physics7030040 - 8 Sep 2025

Abstract

We demonstrate the possibility of generation of zonal (shear) flows in a rotating self-gravitating fluid. A set of equations describing the nonlinear interaction between a large-scale zonal flow (ZF) and a small-scale drift-gravity wave is derived. A nonlinear dispersion relation is obtained, from [...] Read more.

We demonstrate the possibility of generation of zonal (shear) flows in a rotating self-gravitating fluid. A set of equations describing the nonlinear interaction between a large-scale zonal flow (ZF) and a small-scale drift-gravity wave is derived. A nonlinear dispersion relation is obtained, from which the possible instability of the ZF follows. The necessary condition for instability in the space of wave numbers of the drift-gravity wave, as well as the instability threshold for the wave amplitude, are obtained. The growth rate of the modulation instability of ZF is found. The generation of ZFs is due to the Reynolds stresses produced by finite amplitude drift-gravity waves. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor Lennart Stenflo on the Occasion of His 85th Birthday: Plasma Physics and Nonlinear Science)

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7 pages, 359 KB

Open AccessCommunication

Charm Quark Evolution in the Quark–Gluon Plasma with Various Quark Contents

by Valeriya Mykhaylova

Physics 2025, 7(3), 39; https://doi.org/10.3390/physics7030039 - 5 Sep 2025

Abstract

The production rate of charm quarks in strongly interacting matter is investigated under various conditions, employing the effective quasiparticle framework. This phenomenological approach treats quarks and gluons as quasiparticles with dynamically generated self-energies linked to the medium. This paper studies thermal production of [...] Read more.

The production rate of charm quarks in strongly interacting matter is investigated under various conditions, employing the effective quasiparticle framework. This phenomenological approach treats quarks and gluons as quasiparticles with dynamically generated self-energies linked to the medium. This paper studies thermal production of charm quarks in hot deconfined matter when those quarks are treated as impurities with a constant mass or as dynamical quarks dressed by the effective mass. When charm quarks are considered quasiparticles, their large (compared to the bare value) mass generates a significant decrease in the production rate in the crossover region. Various initial conditions for the evolution of the system are applied, showing that lower initial temperature leads to the continual suppression of the charm quark production rate, which appears in line with the previously reported estimate at certain values of the initial parameters. Full article

(This article belongs to the Special Issue High Energy Heavy Ion Physics—Zimányi School 2024)

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22 pages, 585 KB

Open AccessArticle

Fragmentation of a Trapped Multi-Species Bosonic Mixture

by Ofir E. Alon and Lorenz S. Cederbaum

Physics 2025, 7(3), 38; https://doi.org/10.3390/physics7030038 - 1 Sep 2025

Abstract

We consider a multi-species mixture of interacting bosons,

N_{1}

bosons of mass

m_{1}

,

N_{2}

bosons of mass

m_{2}

, and

N_{3}

bosons of mass

m_{3}

, in a harmonic trap with frequency

ω

. The corresponding [...] Read more.

We consider a multi-species mixture of interacting bosons,

N_{1}

bosons of mass

m_{1}

,

N_{2}

bosons of mass

m_{2}

, and

N_{3}

bosons of mass

m_{3}

, in a harmonic trap with frequency

ω

. The corresponding intra-species interaction strengths are

λ_{11}

,

λ_{22}

, and

λ_{33}

, and the inter-species interaction strengths are

λ_{12}

,

λ_{13}

, and

λ_{23}

. When the shape of all interactions is harmonic, the system corresponds to the generic multi-species harmonic-interaction model, which is exactly solvable. We start by solving the many-particle Hamiltonian and concisely discussing the ground-state wavefunction and energy in explicit forms as functions of all parameters, the masses, numbers of particles, and the intra-species and inter-species interaction strengths. We then explicitly compute the reduced one-particle density matrices for all the species and diagonalize them, thus generalizing the treatment by the authors earlier. The respective eigenvalues determine the degree of fragmentation of each species. As an application, we focus on phenomena that do not arise in the corresponding single-species or two-species systems. For instance, we consider a mixture of two kinds of bosons in a bath made by a third kind, controlling the fragmentation of the former by coupling to the latter. Another example exploits the possibility of different connectivities (i.e., which species interacts with which species) in the mixture, and demonstrates how the fragmentation of species 3 can be manipulated by the interaction between species 1 and species 2, when species 3 and 1 do not interact with each other. We highlight the properties of fragmentation that only appear in the multi-species mixture. Further applications are briefly discussed. Full article

(This article belongs to the Special Issue Complexity in High Energy and Statistical Physics)

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18 pages, 5781 KB

Open AccessArticle

Effect of Various Factors on the Accuracy of Determining the Planck Constant in a Student Physics Laboratory

by Stanisław A. Różański

Physics 2025, 7(3), 37; https://doi.org/10.3390/physics7030037 - 15 Aug 2025

Abstract

The Planck constant is a fundamental parameter of nature that appears in the description of phenomena on a microscopic scale. Its origin is associated with an explanation of the distribution of the blackbody spectrum performed by Max Planck. This constant stands the basis [...] Read more.

The Planck constant is a fundamental parameter of nature that appears in the description of phenomena on a microscopic scale. Its origin is associated with an explanation of the distribution of the blackbody spectrum performed by Max Planck. This constant stands the basis for the definition of the International System of Units (SI), and, in particular, the new mass definition. This paper presents different methods for determining the Planck constant based on phenomena such as blackbody radiation, light diffraction through a single slit, the current–voltage characteristics of a light-emitting diode, the photoelectric phenomenon, and the hydrogen atom spectrum in the visible range. The Planck constant was measured using instruments in a stationary laboratory and via remote access. The influence of various factors on the accuracy of the measurements was determined, and the consistency of the obtained results with the accepted value of the Planck constant are examined and discussed. Full article

(This article belongs to the Section Physics Education)

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13 pages, 277 KB

Open AccessArticle

New Conformally Invariant Born–Infeld Models and Geometrical Currents

by Diego Julio Cirilo-Lombardo

Physics 2025, 7(3), 36; https://doi.org/10.3390/physics7030036 - 13 Aug 2025

Abstract

A new conformally invariant gravitational generalization of the Born–Infeld (BI) model is proposed and analyzed from the point of view of symmetries. Taking a geometric identity involving the determinant functions det

f (B_{μ ν}, F_{μ ν})

with the Bach [...] Read more.

A new conformally invariant gravitational generalization of the Born–Infeld (BI) model is proposed and analyzed from the point of view of symmetries. Taking a geometric identity involving the determinant functions det

f (B_{μ ν}, F_{μ ν})

with the Bach

B_{μ ν}

and the electromagnetic field

F_{μ ν}

tensors (with the 4-dimensional Greek letter indexes), two characteristic geometrical Lagrangian densities (Lagrangians) are derived: the first Lagrangian being the square root of the determinant function

\sqrt{|det (B_{μ ν} + F_{μ ν})|}

(reminiscent of the standard BI model) and the second Lagrangian being the fourth root

\sqrt[4]{g det (B_{α γ} B_{β}^{γ} + F_{α γ} F_{β}^{γ})}

. It is shown, after explicit computation of the gravitational equations, that the square-root model is incompatible with the inclusion of the electromagnetic tensor, consequently forcing the nullity of

F_{μ ν}

. In sharp contrast, the traceless fourth-root model is fully compatible and a natural ansatz of the type

B_{μ ρ} B_{ν}^{ρ} \propto Ω (x) g_{μ ν}

(conformal-Killing), with

Ω

the conformal factor and x the 4-coordinate, can be considered. Among other essential properties, the geometrical conformal Lagrangian of the fourth-root type is self-similar with respect to the determinant g of the metric tensor

g_{μ ν}

and can be extended to non-Abelian fields in a way similar to the model developed by the author earlier. This self-similarity is related to the conformal properties of the model, such as the Bach currents or flows presumably of a topological origin. Possible applications and comparisons with other models are briefly discussed. Full article

(This article belongs to the Special Issue Beyond the Standard Models of Physics and Cosmology: 2nd Edition)

21 pages, 347 KB

Open AccessArticle

The Classical Geometry of Chaotic Green Functions and Wigner Functions

by Alfredo M. Ozorio de Almeida

Physics 2025, 7(3), 35; https://doi.org/10.3390/physics7030035 - 5 Aug 2025

Abstract

Semiclassical (SC) approximations for various representations of a quantum state are constructed on a single (Lagrangian) surface in the phase space but such surface is not available for chaotic systems. An analogous evolution surface underlies SC representations of the evolution operator, albeit in [...] Read more.

Semiclassical (SC) approximations for various representations of a quantum state are constructed on a single (Lagrangian) surface in the phase space but such surface is not available for chaotic systems. An analogous evolution surface underlies SC representations of the evolution operator, albeit in a doubled phase space. Here, it is shown that corresponding to the Fourier transform on a unitary operator, represented as a Green function or spectral Wigner function, a Legendre transform generates a resolvent surface as the classical basis for SC representations of the resolvent operator in the double-phase space, independently of the integrable or chaotic nature of the system. This surface coincides with derivatives of action functions (or generating functions) depending on the choice of appropriate coordinates, and its growth departs from the energy shell following trajectories in the double-phase space. In an initial study of the resolvent surface based on its caustics, its complex nature is revealed to be analogous to a multidimensional sponge. Resummation of the trace of the resolvent in terms of linear combinations of periodic orbits, known as pseudo orbits or composite orbits, provides a cutoff to the SC sum at the Heisenberg time. Here, it is shown that the corresponding actions for higher times can be approximately included within true secondary periodic orbits, in which heteroclinic orbits join multiple windings of relatively short periodic orbits into larger circuits. Full article

(This article belongs to the Special Issue A Themed Issue in Honor of Professor Viktor Dodonov—55 Years in Quantum Physics)

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13 pages, 3474 KB

Open AccessArticle

Energy Dispersion Relationship and Hofstadter Butterfly of Triangle and Rectangular Moiré Patterns in Tight Binding States

by Ziheng Li, Jiangwei Liu, Xiaoxiao Zheng, Yu Sun, Nan Han, Liang Wang, Muyang Li, Lei Han, Safia Khan, S. Hassan M. Jafri, Klaus Leifer, Yafei Ning and Hu Li

Physics 2025, 7(3), 34; https://doi.org/10.3390/physics7030034 - 5 Aug 2025

Abstract

Herein, the energy dispersion relationship and the density of states of triangular and rectangular moiré patterns are investigated using a tight binding model. Their characteristics of Hofstadter butterflies under different magnetic fields are also examined. The results indicate that, by analyzing different moiré [...] Read more.

Herein, the energy dispersion relationship and the density of states of triangular and rectangular moiré patterns are investigated using a tight binding model. Their characteristics of Hofstadter butterflies under different magnetic fields are also examined. The results indicate that, by analyzing different moiré superlattices, Hofstadter butterflies arising from different moiré pattern structures are obtained, exhibiting considerable fractal characteristics and self-similarities. Moreover, it is also observed that under an alternating magnetic field, the redistribution of electronic states leads to a significant change in the density of states curve, and the Van Hove peak changes with the increase in magnetic field intensity. This study enriches the understanding of the electronic behavior of moiré systems, but it also provides multiple potential application directions for future technological development. Full article

(This article belongs to the Section Statistical Physics and Nonlinear Phenomena)

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26 pages, 4856 KB

Open AccessArticle

PREFACE: A Search for Long-Lived Particles at the Large Hadron Collider

by Burak Hacisahinoglu, Suat Ozkorucuklu, Maksym Ovchynnikov, Michael G. Albrow, Aldo Penzo and Orhan Aydilek

Physics 2025, 7(3), 33; https://doi.org/10.3390/physics7030033 - 1 Aug 2025

Abstract

The Standard Model (SM) fails to explain many problems (neutrino masses, dark matter, and matter–antimatter asymmetry, among others) that may be resolved with new particles beyond the SM. No observation of such new particles may be explained either by their exceptionally high mass [...] Read more.

The Standard Model (SM) fails to explain many problems (neutrino masses, dark matter, and matter–antimatter asymmetry, among others) that may be resolved with new particles beyond the SM. No observation of such new particles may be explained either by their exceptionally high mass or by considerably small coupling to SM particles. The latter case implies relatively long lifetimes. Such long-lived particles (LLPs) then to have signatures different from those of SM particles. Searches in the “central region” are covered by the LHC general purpose experiments. The forward small angle region far from the interaction point (IP) is unexplored. Such particles are expected to have the energy as large as E =

O

(1 TeV) and Lorentz time dilation factor

γ = E / m \approx 10^{2}

–

10^{3}

(with m the particle mass) hence long enough decay distances. A new class of specialized LHC detectors dedicated to LLP searches has been proposed for the forward regions. Among these experiments, FASER is already operational, and FACET is under consideration at a location 100 m from the LHC IP5 (the CMS detector intersection). However, some features of FACET require a specially enlarged beam pipe, which cannot be implemented for LHC Run 4. In this study, we explore a simplified version of the proposed detector PREFACE compatible with the standard LHC beam pipe in the HL-LHC Run 4. Realistic Geant4 simulations are performed and the background is evaluated. An initial analysis of the physics potential with the PREFACE geometry indicates that several significant channels could be accessible with sensitivities comparable to FACET and other LLP searches. Full article

(This article belongs to the Section High Energy Physics)

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15 pages, 6245 KB

Open AccessArticle

Investigation of Charging Effect on an Isolated Conductor Based on a Monte Carlo Simulation

by Haotian Chen, Shifeng Mao and Zejun Ding

Physics 2025, 7(3), 32; https://doi.org/10.3390/physics7030032 - 1 Aug 2025

Abstract

We report calculations of charging effect on an isolated conductor, gold nanosphere, under electron beam bombardment at primary electron energies of 0.1–10 keV based on an up-to-date Monte Carlo simulation method. The calculations consider electron flow in sample, in which the electron yield [...] Read more.

We report calculations of charging effect on an isolated conductor, gold nanosphere, under electron beam bombardment at primary electron energies of 0.1–10 keV based on an up-to-date Monte Carlo simulation method. The calculations consider electron flow in sample, in which the electron yield is almost equivalent to the case when the electron flow is not considered. The electron yields and charging spatial distribution are obtained. For comparison, the calculation for bulk conductor is also performed, for which the time average of electric potential is found to reproduce the law of electrostatics. Full article

(This article belongs to the Section Applied Physics)

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12 pages, 736 KB

Open AccessArticle

Hybrid Framework of Fermi–Dirac Spin Hydrodynamics

by Zbigniew Drogosz

Physics 2025, 7(3), 31; https://doi.org/10.3390/physics7030031 - 1 Aug 2025

Cited by 1

Abstract

The paper outlines the hybrid framework of spin hydrodynamics, combining classical kinetic theory with the Israel–Stewart method of introducing dissipation. The local equilibrium expressions for the baryon current, the energy–momentum tensor, and the spin tensor of particles with spin 1/2 following the Fermi–Dirac [...] Read more.

The paper outlines the hybrid framework of spin hydrodynamics, combining classical kinetic theory with the Israel–Stewart method of introducing dissipation. The local equilibrium expressions for the baryon current, the energy–momentum tensor, and the spin tensor of particles with spin 1/2 following the Fermi–Dirac statistics are obtained and compared with the earlier derived versions where the Boltzmann approximation was used. The expressions in the two cases are found to have the same form, but the coefficients are shown to be governed by different functions. The relative differences between the tensor coefficients in the Fermi–Dirac and Boltzmann cases are found to grow exponentially with the baryon chemical potential. In the proposed formalism, nonequilibrium processes are studied including mathematically possible dissipative corrections. Standard conservation laws are applied, and the condition of positive entropy production is shown to allow for the transfer between the spin and orbital parts of angular momentum. Full article

(This article belongs to the Special Issue High Energy Heavy Ion Physics—Zimányi School 2024)

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14 pages, 959 KB

Open AccessArticle

Exploring Hidden Sectors with Two-Particle Angular Correlations at Future e⁺e⁻ Colliders

by Emanuela Musumeci, Adrián Irles, Redamy Pérez-Ramos, Imanol Corredoira, Edward Sarkisyan-Grinbaum, Vasiliki A. Mitsou and Miguel Ángel Sanchis-Lozano

Physics 2025, 7(3), 30; https://doi.org/10.3390/physics7030030 - 22 Jul 2025

Abstract

Future

e^{+} e^{-}

colliders are expected to play a fundamental role in measuring Standard Model (SM) parameters with unprecedented precision and in probing physics beyond the SM (BSM). This study investigates two-particle angular correlation distributions involving final-state SM charged hadrons. Unexpected [...] Read more.

Future

e^{+} e^{-}

colliders are expected to play a fundamental role in measuring Standard Model (SM) parameters with unprecedented precision and in probing physics beyond the SM (BSM). This study investigates two-particle angular correlation distributions involving final-state SM charged hadrons. Unexpected correlation structures in these distributions is considered to be a hint for new physics perturbing the QCD partonic cascade and thereby modifying azimuthal and (pseudo)rapidity correlations. Using Pythia8 Monte Carlo generator and fast simulation, including selection cuts and detector effects, we study potential structures in the two-particle angular correlation function. We adopt the QCD-like Hidden Valley (HV) scenario as implemented in Pythia8 generator, with relatively light HV v-quarks (below about 100 GeV), to illustrate the potential of this method. Full article

(This article belongs to the Section High Energy Physics)

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11 pages, 1218 KB

Open AccessCommunication

Spin Polarization Crossing a Heterostructure of a Ferromagnetic/Semiconductor-Based Rashba Spin–Orbit Interaction: Tight Binding Approach

by Aek Jantayod

Physics 2025, 7(3), 29; https://doi.org/10.3390/physics7030029 - 17 Jul 2025

Abstract

The spin polarization of current in a conventional ferromagnetic and semiconductor-based Rashba spin–orbit interaction (RSOI) in an infinite two-dimensional system and the electrical properties of the junction are described using the square lattice model. In particular, a suitable approach is devised to compute [...] Read more.

The spin polarization of current in a conventional ferromagnetic and semiconductor-based Rashba spin–orbit interaction (RSOI) in an infinite two-dimensional system and the electrical properties of the junction are described using the square lattice model. In particular, a suitable approach is devised to compute the particle transport characteristics in the junction, taking into consideration the interface quality. It is found that the spin polarization becomes strongly reliant on the spin-flip scattering potential at applied voltages close to the crossings of the semiconductor-based RSOI band. On the other hand, in the voltage near the middle band, the spin polarization of current is found to remain modest and not influenced by either the spin-flip or non-spin-flip scattering potentials. Full article

(This article belongs to the Section Classical Physics)

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32 pages, 3005 KB

Open AccessReview

Photophysical Process of Hypocrellin-Based Photodynamic Therapy: An Efficient Antimicrobial Strategy for Overcoming Multidrug Resistance

by Pazhani Durgadevi, Koyeli Girigoswami and Agnishwar Girigoswami

Physics 2025, 7(3), 28; https://doi.org/10.3390/physics7030028 - 15 Jul 2025

Cited by 1

Abstract

The emergence of multidrug-resistant (MDR) bacteria and biofilm-associated infections has created a significant hurdle for conventional antibiotics, prompting the exploration of alternative strategies. Photodynamic therapy (PDT), a technique that utilizes photosensitizers activated by light to produce ROS, has emerged as a beacon of [...] Read more.

The emergence of multidrug-resistant (MDR) bacteria and biofilm-associated infections has created a significant hurdle for conventional antibiotics, prompting the exploration of alternative strategies. Photodynamic therapy (PDT), a technique that utilizes photosensitizers activated by light to produce ROS, has emerged as a beacon of hope in the fight against MDR microorganisms. Among the natural photosensitizers, hypocrellins (A and B) have shown remarkable potential with their dual-mode photodynamic action, generating ROS via both Type I (electron transfer) and Type II (singlet oxygen) pathways. This unique action disrupts bacterial biofilms and inactivates MDR pathogens. The amphiphilic nature of hypocrellins further enhances their promise, enabling deep biofilm penetration and ensuring potent antibacterial effects even in hypoxic environments, surpassing the capabilities of synthetic photosensitizers. This study critically examines the antimicrobial properties of hypocrellin-based PDT, emphasizing its mechanisms, advantages over traditional antibiotics, and effectiveness against MDR pathogens. Comparative analysis with other photosensitizers, the role of nanotechnology-enhanced delivery systems, and future clinical applications are explored. Its combination with nanotechnology enhances therapeutic outcomes, providing a viable alternative to conventional antibiotics. Further clinical research is essential to optimize its application and integration into antimicrobial treatment protocols. Full article

(This article belongs to the Section Biophysics and Life Physics)

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12 pages, 3178 KB

Open AccessArticle

Terahertz Optoelectronic Properties of Monolayer MoS₂ in the Presence of CW Laser Pumping

by Ali Farooq, Wen Xu, Jie Zhang, Hua Wen, Qiujin Wang, Xingjia Cheng, Yiming Xiao, Lan Ding, Altayeb Alshiply Abdalfrag Hamdalnile, Haowen Li and Francois M. Peeters

Physics 2025, 7(3), 27; https://doi.org/10.3390/physics7030027 - 14 Jul 2025

Cited by 1

Abstract

Monolayer (ML) molybdenum disulfide (MoS₂) is a typical valleytronic material which has important applications in, for example, polarization optics and information technology. In this study, we examine the effect of continuous wave (CW) laser pumping on the basic optoelectronic properties of [...] Read more.

Monolayer (ML) molybdenum disulfide (MoS₂) is a typical valleytronic material which has important applications in, for example, polarization optics and information technology. In this study, we examine the effect of continuous wave (CW) laser pumping on the basic optoelectronic properties of ML MoS₂ placed on a sapphire substrate, where the pump photon energy is larger than the bandgap of ML MoS₂. The pump laser source is provided by a compact semiconductor laser with a 445 nm wavelength. Through the measurement of THz time-domain spectroscopy, we obtain the complex optical conductivity for ML MoS₂, which are found to be fitted exceptionally well with the Drude–Smith formula. Therefore, we expect that the reduction in conductivity in ML MoS₂ is mainly due to the effect of electronic backscattering or localization in the presence of the substrate. Meanwhile, one can optically determine the key electronic parameters of ML MoS₂, such as the electron density n_e, the intra-band electronic relaxation time τ, and the photon-induced electronic localization factor c. The dependence of these parameters upon CW laser pump intensity is examined here at room temperature. We find that 445 nm CW laser pumping results in the larger n_e, shorter τ, and stronger c in ML MoS₂ indicating that laser excitation has a significant impact on the optoelectronic properties of ML MoS₂. The origin of the effects obtained is analyzed on the basis of solid-state optics. This study provides a unique and tractable technique for investigating photo-excited carriers in ML MoS₂. Full article

(This article belongs to the Section Applied Physics)

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9 pages, 244 KB

Open AccessCommunication

Derivation of the Ray Equation from Snell’s Law

by Carmen Toro-Castillo, Joel Cervantes-Lozano, David I. Serrano-García and Héctor O. González-Ochoa

Physics 2025, 7(3), 26; https://doi.org/10.3390/physics7030026 - 9 Jul 2025

Abstract

The one-dimensional ray equation, the differential description of Fermat’s principle, is deduced directly from Snell’s law using two methods. In the first method, we obtain the ray equation from a differential equation relating the spatial coordinates derivative with the index of refraction field. [...] Read more.

The one-dimensional ray equation, the differential description of Fermat’s principle, is deduced directly from Snell’s law using two methods. In the first method, we obtain the ray equation from a differential equation relating the spatial coordinates derivative with the index of refraction field. In the second method, the ray equation is deduced from the proper generalization of Snell’s law for a refractive field, that is, a differential equation relating the index of refraction field and the refraction angle. Additionally, we used an intermediate expression of the first method to find a straightforward analytical solution of the ray path to an inferior mirage. Full article

(This article belongs to the Section Physics Education)

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19 pages, 23214 KB

Open AccessArticle

Quantum Scattering by Multiple Slits—A Lippmann–Schwinger Approach

by Rafael M. Fortiny, Matheus E. Pereira and Alexandre G. M. Schmidt

Physics 2025, 7(3), 25; https://doi.org/10.3390/physics7030025 - 1 Jul 2025

Abstract

We investigate the non-relativistic scattering of a plane wave by a vertical segment formulating the problem in terms of the Lippmann–Schwinger equation in two spatial dimensions. Adjusting the coupling strength function we show how to implement the scattering by a system of multiple [...] Read more.

We investigate the non-relativistic scattering of a plane wave by a vertical segment formulating the problem in terms of the Lippmann–Schwinger equation in two spatial dimensions. Adjusting the coupling strength function we show how to implement the scattering by a system of multiple slits and by a Cantor set. We present detailed calculations of the scattered wave function for the line segment, as well as for the single, double, and multiple slits. We define reflection and transmission functions that are position-dependent in a defined region. From these results, we obtain the probability densities and differential and total cross-sections for these problems. Full article

(This article belongs to the Section Classical Physics)

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19 pages, 568 KB

Open AccessArticle

Testing the Double-Logarithmic Asymptotic Gluon Density in Ultraperipheral Heavy-Ion Collisions at the Large Hadron Collider

by Daniel Almeida Fagundes and Magno V. T. Machado

Physics 2025, 7(3), 24; https://doi.org/10.3390/physics7030024 - 25 Jun 2025

Cited by 1

Abstract

In this paper, we analyze the application of an analytical gluon distribution based on double-asymptotic scaling to the photoproduction of vector mesons in coherent

p p

,

p A

, and

A A

collisions at LHC energies, using the color dipole formalism. Predictions [...] Read more.

In this paper, we analyze the application of an analytical gluon distribution based on double-asymptotic scaling to the photoproduction of vector mesons in coherent

p p

,

p A

, and

A A

collisions at LHC energies, using the color dipole formalism. Predictions for the rapidity distribution are presented for

ρ^{0}

,

J / ψ

,

ψ (2 S)

, and

Υ (1 S)

mesons photoproduction. An analysis of the uncertainties associated with different implementations of the dipole–proton amplitude is performed. The vector meson photoproduction accompanied by electromagnetic dissociation is also analyzed. Full article

(This article belongs to the Section High Energy Physics)

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