International Journal of Physics | Vol. 17, No. 8, August 2026 | pp. 89–96
DOI: 10.46882/2026/IJP/000200
Research Article
Title: Phonon Dispersion and Thermal Conductivity of Monolayer Black Phosphorus Under Axial Tensile Strain
Names of Authors: Y. W. Zhang¹, K. N. Singh²
Authors’ Affiliations:
¹ Department of Physics, Tsinghua University, Beijing, China
² Department of Mechanical Engineering, Indian Institute of Technology, New Delhi, India
Abstract: Controlling heat transport at the nanoscale is essential for managing thermal dissipation in next-generation nanoelectronic devices. This study investigates the phonon dispersion relations and lattice thermal conductivity of black phosphorus nanoribbons subjected to uniaxial tensile strain. We performed comprehensive molecular dynamics simulations using an optimized empirical potential combined with the Green-Kubo formal mathematical framework. Calculations were conducted at an equilibrium temperature of 300.0 K under mechanical tensile strains varying from 0.0% to 12.0%. Our structural models revealed that the lattice thermal conductivity of an unstrained ribbon (width = 2.5 nm) is approximately 1420.0 W/m-K along the zigzag direction. Applying a 10.0% tensile strain caused a sharp 58.0% reduction in thermal conductivity for armchair configurations, whereas zigzag configurations exhibited a less severe 42.0% decrease. Analysis of the phonon dispersion curves showed that uniaxial strain significantly softens the acoustic phonon modes, particularly the flexural out-of-plane (ZA) and transverse acoustic (TA) branches. Specifically, the frequency of the ZA mode at the Brillouin zone boundary decreased by 24.5% under 8.0% strain. This mode softening reduces the phonon group velocities and increases the Umklapp scattering rates due to enhanced lattice anharmonicity. The calculated phonon lifetime dropped from 4.2 ps to 1.8 ps at room temperature under maximum strain conditions. These results demonstrate that mechanical strain engineering provides an effective method for tuning thermal properties in phosphorene-based nanoelectronics and thermoelectric systems.
Keywords: Phosphorene nanoribbons; Thermal conductivity; Phonon dispersion; Molecular dynamics; Tensile strain; Umklapp scattering
Manuscript Timeline: Received: April 25, 2026 / Revised: June 03, 2026 / Accepted: June 25, 2026 / Published: August 14, 2026
Citation: Zhang, Y. W., & Singh, K. N. (2026). Phonon Dispersion and Thermal Conductivity of Monolayer Black Phosphorus Under Axial Tensile Strain. International Journal of Physics, 17(8), 89–96.
International Journal of Physics | Vol. 17, No. 8, August 2026 | pp. 81–88
DOI: 10.46882/2026/IJP/000199
Research Article
Title: Relativistic Jet Deceleration and Magnetohydrodynamic Instabilities in Inhomogeneous Interstellar Medium
Names of Authors: G. V. Bruno¹, C. M. Martinez², L. A. O’Connor³
Authors’ Affiliations:
¹ Department of Astrophysics, University of Bologna, Bologna, Italy
² Instituto de Astrofísica de Andalucía, CSIC, Granada, Spain
³ School of Cosmic Physics, Dublin Institute for Advanced Studies, Dublin, Ireland
Abstract: The deceleration of relativistic jets in gamma-ray bursts (GRBs) and active galactic nuclei (AGN) depends heavily on the density profile of the surrounding ambient medium. We performed high-resolution two-dimensional relativistic hydrodynamic simulations to model jet propagation into an inhomogeneous interstellar medium. The ambient medium was configured with periodic density fluctuations ranging over two orders of magnitude (from 0.01 to 1.00 particles/cm³). The initial jet Lorentz factor was set to W = 50, and the jet-to-ambient matter density ratio was 0.001. Our numerical results show that when the relativistic jet impacts high-density clouds, it triggers strong reverse shocks that propagate backward into the jet core. These reverse shocks cause significant kinetic energy dissipation, reducing the bulk Lorentz factor by up to 35.0% within a propagation distance of 1.0 pc. The interaction creates high-pressure regions and severe Kelvin-Helmholtz instabilities along the jet boundary. These instabilities lead to strong turbulent mixing and the formation of a prominent forward shock cocoon. We extracted synthetic synchrotron emission profiles from the simulated pressure and magnetic field distributions. The light curves exhibit distinct, short-term flux variability and temporal variability indices fluctuating between -1.1 and -1.5 during the deceleration phase. These simulated emission spikes match the early-time X-ray and optical afterglow flares observed in several astrophysical events. Consequently, these findings offer a coherent structural explanation for the erratic light curves recorded by modern space telescopes.
Keywords: Relativistic hydrodynamics; Gamma-ray bursts; Active galactic nuclei; Interstellar medium; Shock waves; Synchrotron emission
Manuscript Timeline: Received: April 22, 2026 / Revised: June 01, 2026 / Accepted: June 22, 2026 / Published: August 14, 2026
Citation: Bruno, G. V., Martinez, C. M., & O’Connor, L. A. (2026). Relativistic Jet Deceleration and Magnetohydrodynamic Instabilities in Inhomogeneous Interstellar Medium. International Journal of Physics, 17(8), 81–88.
International Journal of Physics | Vol. 17, No. 8, August 2026 | pp. 73–80
DOI: 10.46882/2026/IJP/000198
Research Article
Title: Thermodynamic Analysis and Efficiency Optimization of Perovskite Intermediate Band Solar Cells
Names of Authors: H. K. Tanaka¹, E. C. Dupont²
Authors’ Affiliations:
¹ Department of Quantum Engineering, Nagoya University, Nagoya, Japan
² Laboratory of Photovoltaics, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
Abstract: Intermediate band solar cells (IBSCs) present a highly promising route to exceed the Shockley-Queisser efficiency limit of single-junction photovoltaic devices. This paper presents a detailed thermodynamic model to evaluate the conversion efficiency limit of formamidinium lead iodide intermediate band solar cells. We systematically evaluated the impacts of radiative and non-radiative recombination rates on device performance under full solar concentration (46,200 suns) and standard one-sun illumination. Our numerical calculations reveal an ideal thermodynamic efficiency limit of 63.2% under full concentration when non-radiative losses are completely suppressed. However, when standard Shockley-Read-Hall non-radiative lifetimes of 1.5 ns are introduced, the maximum achievable efficiency drops sharply to 38.5%. To mitigate these non-radiative losses, we simulated a graded band gap host structure that enhances carrier extraction from the intermediate band to the conduction band. The optimized device design yields a short-circuit current density of 39.4 mA/cm² and an open-circuit voltage of 1.12 V under one-sun conditions. We also analyzed the thermal stability of the intermediate band population between 200.0 K and 400.0 K. The results demonstrate that thermal carrier escape significantly degrades sub-bandgap photon absorption above 280.0 K. This degradation emphasizes the critical need for deep potential wells exceeding 0.3 eV. These detailed thermodynamic insights provide valuable engineering guidelines for structural optimization in third-generation high-efficiency perovskite photovoltaics.
Keywords: Photovoltaics; Perovskites; Intermediate band solar cells; Thermodynamic efficiency; Recombination lifetime; Solar energy
Manuscript Timeline: Received: April 18, 2026 / Revised: May 28, 2026 / Accepted: June 20, 2026 / Published: August 14, 2026
Citation: Tanaka, H. K., & Dupont, E. C. (2026). Thermodynamic Analysis and Efficiency Optimization of Perovskite Intermediate Band Solar Cells. International Journal of Physics, 17(8), 73–80.
International Journal of Physics | Vol. 17, No. 8, August 2026 | pp. 65–72
DOI: 10.46882/2026/IJP/000197
Research Article
Title: Anisotropic Magnetoresistance and Electronic Structure of Cobalt-Doped Monolayer Molybdenum Disulfide
Names of Authors: M. R. Al-Mansoor¹, S. J. Thornton², A. L. Rostov³
Authors’ Affiliations:
¹ Department of Physics, Condensed Matter Research Laboratory, University of Cambridge, Cambridge, UK
² Centre for Advanced Materials Science, Monash University, Melbourne, Australia
³ Institute of Solid State Physics, Russian Academy of Sciences, Moscow, Russia
Abstract: This study investigates the anisotropic magnetoresistance (AMR) and electronic band structure of cobalt-doped monolayer molybdenum disulfide (MoS²) synthesized via chemical vapor deposition. We deposited films with varying cobalt concentrations (from 1.0% to 7.0% atomic weight) on strontium titanate substrates. X-ray diffraction patterns confirmed a high-quality phase with no visible secondary phase segregations. Electrical transport measurements were conducted across a wide temperature range from 2.0 K to 300.0 K. A maximum negative magnetoresistance of 4.5% was observed at 5.0 K under an applied magnetic field of 5.0 T. This magnetotransport behaviour decreases monotonically as the temperature increases toward room temperature. Density functional theory calculations indicate that the cobalt 3d states hybridize significantly with the molybdenum 3d and sulfur 3p bands. This hybridization induces a spin-polarized density of states at the Fermi level. The spin polarization value was calculated to be approximately 42.0% for the 5.0% cobalt-doped sample. Optical absorption spectroscopy revealed a systematic redshift in the optical band gap from 1.85 eV to 1.65 eV with increasing cobalt content. This shift confirms the substitution of molybdenum ions by cobalt ions within the crystal lattice. Hall effect measurements revealed n-type carrier concentrations ranging from 1.2 x 10¹⁹ to 4.8 x 10²⁰ cm⁻³. These findings suggest that the observed ferromagnetism is carrier-mediated, aligning with the bound magnetic polaron model. The robust spin-polarized transport properties identified in these dilute magnetic semiconductor films make them highly viable candidates for room-temperature spintronic applications.
Keywords: Dilute magnetic semiconductors; Monolayers; Magnetoresistance; Spintronics; Density functional theory; Band gap tuning
Manuscript Timeline: Received: April 12, 2026 / Revised: May 24, 2026 / Accepted: June 15, 2026 / Published: August 14, 2026
Citation: Al-Mansoor, M. R., Thornton, S. J., & Rostov, A. L. (2026). Anisotropic Magnetoresistance and Electronic Structure of Cobalt-Doped Monolayer Molybdenum Disulfide. International Journal of Physics, 17(8), 65–72.
International Journal of Physics | Vol. 17, No. 8, August 2026 | pp. 57–64
DOI: 10.46882/2026/IJP/000196
Research Article
Title: Elasticity Attributes and Phase Transformations in Ultra-Incompressible Molybdenum Tetraboride Polytypes
Names of Authors: V. I. Morozov¹, P. J. O’Connor²
Authors’ Affiliations:
¹ Institute of High Pressure Physics, Russian Academy of Sciences, Troitsk, Russia
² Department of Civil and Environmental Engineering, University College Cork, Cork, Ireland
Abstract: Evaluating ultra-incompressible structural alloys capable of maintaining structural stability under immense mechanical loading parameters is vital for industrial tool fabrication, ballistic armor design, and high-pressure geoscience anvil components. This paper investigates high-pressure elasticity profiles and monitors structural phase transformations in hexagonal and orthorhombic molybdenum tetraboride (MoB4) polytypes up to hydrostatic pressures of 160.0 GPa. We performed first-principles density functional theory computations within the generalized gradient approximation framework across compressed atomic configurations. At zero pressure, the calculated bulk modulus is B0 = 315.0 GPa, with an elastic pressure derivative value of B0' = 4.12, matching experimental diamond anvil cell measurements within a 1.2% margin. The single-crystal elastic constants (C11, C22, C33, C44, C55, and C66) increase monotonically under uniform compression paths, satisfying all Born mechanical stability metrics across the entire tested pressure range. The directional compressibility paths reveal that the crystal c-axis displays exceptional stiffness due to short, covalent molybdenum-boron bonds interlocking the structural rows. Electronic density calculations confirm a persistent metallic profile under ultra-high structural strain.
Keywords: Molybdenum tetraboride; density functional theory; elastic constants; high pressure; structural stability; polytypes
Manuscript Timeline: Received: May 12, 2026; Revised: July 03, 2026; Accepted: July 25, 2026; Published: August 14, 2026
Citation: Morozov, V. I., & O’Connor, P. J. (2026). Elasticity Attributes and Phase Transformations in Ultra-Incompressible Molybdenum Tetraboride Polytypes. International Journal of Physics, 17(8), 57–64.
International Journal of Physics | Vol. 17, No. 7, July 2026 | pp. 49–56
DOI: 10.46882/2026/IJP/000195
Research Article
Title: Optical Soliton Intabilities and Phase Control in Non-Local Polymeric Metamaterials with Higher-Order Saturable Responses
Names of Authors: L. K. Rousseau¹, G. R. Davies²
Authors’ Affiliations:
¹ Laboratoire de Physique des Plasmas, École Polytechnique, Palaiseau, France
² School of Physics and Astronomy, University of St Andrews, St Andrews, UK
Abstract: Controlling ultra-short laser pulse propagation tracks and eliminating high-power beam filamentation are critical operational tasks when developing polymer-based photonic components, all-optical computing routers, and microcircuit routers. This study models optical soliton dynamics and characterises modulation instability profiles inside non-local polymeric metamaterials exhibiting higher-order saturable electronic non-linearities. We solved the generalized non-linear Schrödinger equations including higher-order perturbation corrections, specifically third-order dispersion, self-steepening, and delayed Raman response steps. The numerical simulations used a variational approach paired with split-step Fourier schemes to extract exact single-soliton and breather solutions. The results demonstrate that high spatial non-locality parameters effectively suppress catastrophic self-focusing collapse nodes by smoothing localized wavefront phase errors. The modulation instability growth rate was tracked against changing spatial perturbation frequencies, highlighting a maximum gain coefficient of g = 2.95 cm⁻¹ under an input beam intensity of 2.2 kW/cm². Expanding the non-locality parameter scales down the maximum instability gain by 70.0%, preventing pulse fragmentation across waveguides.
Keywords: Nonlinear optics; spatial solitons; nonlinear Schrödinger equation; modulational instability; non-local media; polymeric metamaterials
Manuscript Timeline: Received: April 15, 2026; Revised: June 02, 2026; Accepted: June 22, 2026; Published: July 15, 2026
Citation: Rousseau, L. K., & Davies, G. R. (2026). Optical Soliton Intabilities and Phase Control in Non-Local Polymeric Metamaterials with Higher-Order Saturable Responses. International Journal of Physics, 17(7), 49–56.