International Journal of Physics | Vol. 6, No. 6, June 2015 | pp. 41–48
DOI: 10.46882/2015/IJP/000062
Research Article
Title: Thermal Conductance Degradation and Phonon Scattering at Graphene-Silicon Interfacial Defect Boundaries
Names of Authors: D. W. Meyer¹, C. H. Jenkins²
Authors’ Affiliations: ¹Institute of Physics, Karlsruher Institut für Technologie, Karlsruhe, Germany; ²Space Sciences Laboratory, University of California, Berkeley, California, USA
Abstract: Dissipating heat efficiently across mismatched material boundaries is a major technical challenge in modern high-power nanoelectronics. This paper uses molecular dynamics simulations to quantify thermal conductance degradation and track phonon wavepacket scattering at defective graphene-silicon (Gr-Si) interfaces. We constructed atomistic models using the optimized Tersoff and Stillinger-Weber potentials, incorporating varying concentrations of interfacial point defects and vacancy networks. Longitudinal and transverse acoustic phonon wavepackets were generated with narrow frequency spreads centered between 3.0 THz and 10.0 THz. The computational data demonstrate that high-frequency acoustic phonons (f greater than 6.0 THz) undergo strong diffuse scattering at the defective interface, dropping the transmission coefficient from 0.74 down to 0.18. This diffuse scattering is driven by localized strain fields and localized interface vibrational modes. The overall interfacial thermal conductance was calculated to decrease by 52.0% when the interfacial defect density scaled from 1.0% to 5.0% at 300.0 K. These molecular dynamics calculations clarify the atomic-scale mechanisms restricting heat carrier propagation, helping engineers design targeted thermal management solutions for graphene-based devices.
Keywords: Thermal conductance; phonon scattering; molecular dynamics; graphene-silicon interface; defect density; nanoelectronics
Manuscript Timeline: Received: March 04, 2015; Revised: April 22, 2015; Accepted: May 10, 2015; Published: June 18, 2015
Citation: Meyer, D. W., & Jenkins, C. H. (2015). Thermal Conductance Degradation and Phonon Scattering at Graphene-Silicon Interfacial Defect Boundaries. International Journal of Physics, 6(6), 41–48.
International Journal of Physics | Vol. 6, No. 5, May 2015 | pp. 33–40
DOI: 10.46882/2015/IJP/000061
Research Article
Title: Relativistic Hydrodynamic Evolution and Elliptic Flow Fluctuations in Asymmetric Deuteron-Gold Collisions
Names of Authors: S. C. O’Brien¹, A. O. Awosika²
Authors’ Affiliations: ¹School of Physics, University College Dublin, Dublin, Ireland; ²Department of Physics, University of Ibadan, Ibadan, Nigeria
Abstract: High-energy asymmetric collisions provide a unique experimental testing ground to study the spatial geometry limits required to form a droplet of quark-gluon plasma. This study presents a relativistic hydrodynamic modeling framework to simulate particle production cascades and evaluate elliptic flow fluctuations in deuteron-gold (d-Au) collisions at a center-of-mass energy of 200.0 GeV per nucleon pair. We utilized a 3+1 dimensional viscous hydrodynamic code coupled with a statistical hadronization module to compute transverse momentum spectra. The initial energy density profiles were generated using a Monte Carlo Glauber model to capture sub-nucleon scale configurations. The numerical simulations show that expanding systems build a substantial radial flow profile, shifting the mean transverse momentum of pions up to 0.75 GeV/c in high-multiplicity events. The calculated elliptic flow coefficient (v²) displays a strong mass-ordering effect, which matches experimental measurements gathered by the PHENIX detector within a ±5.5% margin. This close agreement suggests that small-scale systems generated in d-Au collisions can achieve brief hydrodynamic collective expansion. These findings help clarify the boundaries of fluid-like behavior in high-energy subatomic particle interactions.
Keywords: Relativistic hydrodynamics; particle production; deuteron-gold collisions; elliptic flow; Glauber model; statistical hadronization
Manuscript Timeline: Received: February 15, 2015; Revised: March 24, 2015; Accepted: April 12, 2015; Published: May 15, 2015
Citation: O’Brien, S. C., & Awosika, A. O. (2015). Relativistic Hydrodynamic Evolution and Elliptic Flow Fluctuations in Asymmetric Deuteron-Gold Collisions. International Journal of Physics, 6(5), 33–40.
International Journal of Physics | Vol. 6, No. 4, April 2015 | pp. 25–32
DOI: 10.46882/2015/IJP/000060
Research Article
Title: Kinetic Modelling of Electron Transport Parameters and Ionization Coefficients in Silane-Hydrogen Plasmas
Names of Authors: D. L. Santos¹, K. N. Gupta²
Authors’ Affiliations: ¹Department of Physics, University of Coimbra, Coimbra, Portugal; ²Department of Physics, Indian Institute of Technology, New Delhi, India
Abstract: Silane-hydrogen (SiH4-H2) gas discharges are widely used in the solar industry to deposit high-quality amorphous silicon thin films for photovoltaic panels. This paper develops a self-consistent kinetic model to evaluate electron transport parameters and calculate ionization coefficients in low-pressure silane-hydrogen mixtures. We solved the electron Boltzmann equation using a multi-term spherical harmonic expansion framework across a wide reduced electric field range (E/N) from 5.0 Td to 600.0 Td. The cross-section dataset included elastic momentum transfer, rotational, vibrational excitation, dissociative attachment, and direct impact ionization processes. Our modeling results show that adding small fractions of silane (from 2.0% to 10.0% by volume) drastically distorts the electron energy distribution function. At E/N = 50.0 Td, the total dissociation rate coefficient increases by an order of magnitude due to the low threshold energy of silane vibrational modes. The calculated electron drift velocities and diffusion coefficients match independent swarm experimental measurements within a tight ±5.0% variance. These kinetic parameters provide essential input data for optimizing industrial plasma-enhanced chemical vapor deposition reactors.
Keywords: Silane plasmas; Boltzmann equation; electron transport; ionization coefficient; chemical vapor deposition; cross-section
Manuscript Timeline: Received: January 04, 2015; Revised: February 18, 2015; Accepted: March 05, 2015; Published: April 10, 2015
Citation: Santos, D. L., & Gupta, K. N. (2015). Kinetic Modelling of Electron Transport Parameters and Ionization Coefficients in Silane-Hydrogen Plasmas. International Journal of Physics, 6(4), 25–32.
International Journal of Physics | Vol. 6, No. 3, March 2015 | pp. 17–24
DOI: 10.46882/2015/IJP/000059
Research Article
Title: Topological Bound States and Robust Spin Transport in Two-Dimensional Quantum Spin Hall Insulators
Names of Authors: J. W. Park¹, M. T. Al-Saeed²
Authors’ Affiliations: ¹Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, South Korea; ²Department of Physics, Faculty of Science, Kuwait University, Safat, Kuwait
Abstract: Quantum spin Hall insulators provide an innovative pathway for developing low-power electronics by supporting backscattering-immune spin transport along their boundaries. This study designs and simulates topological bound states and robust spin transport within a two-dimensional honeycombed lattice of bismuth-pretreated silicon thin films. We computed the electronic band structures using the relativistic tight-binding method across the Brillouin zone. The strong intrinsic spin-orbit coupling breaks the electronic degeneracy at the Dirac valleys, creating a bulk topological band gap with a width of 0.18 eV. We calculated a non-zero spin Chern number of Cs = +1, verifying the non-trivial topological character of the system. To demonstrate transport robustness, we simulated spin-polarized electron wavepacket propagation past single-atom vacancies and line defect boundaries. The edge mode bypassed these structural obstacles with a high transmission efficiency of 99.4% ± 0.2%, showing zero backscattering due to time-reversal symmetry protections. These findings provide solid engineering targets for building backscattering-immune spintronic transistors, quantum data pathways, and integrated spin-logic circuits.
Keywords: Topological insulators; quantum spin Hall effect; spin-orbit coupling; tight-binding method; edge states; spintronics
Manuscript Timeline: Received: December 12, 2014; Revised: January 20, 2015; Accepted: February 07, 2015; Published: March 13, 2015
Citation: Park, J. W., & Al-Saeed, M. T. (2015). Topological Bound States and Robust Spin Transport in Two-Dimensional Quantum Spin Hall Insulators. International Journal of Physics, 6(3), 17–24.
International Journal of Physics | Vol. 6, No. 2, February 2015 | pp. 9–16
DOI: 10.46882/2015/IJP/000058
Research Article
Title: Elasticity Profiles and High-Pressure Phase Transitions in Ultra-Incompressible Rhenium Diboride
Names of Authors: V. I. Morozov¹, E. M. Gallagher²
Authors’ Affiliations: ¹Institute of High Pressure Physics, Russian Academy of Sciences, Troitsk, Russia; ²School of Physics, Trinity College Dublin, Dublin, Ireland
Abstract: Developing ultra-incompressible structural materials capable of operating under extreme mechanical stress is vital for specialized industrial machining and deep-earth simulation components. This paper investigates the high-pressure elastic profiles and monitors structural phase transitions in hexagonal rhenium diboride (ReB²) up to hydrostatic pressures of 150.0 GPa. We performed first-principles density functional theory computations within the generalized gradient approximation framework. At zero pressure, the calculated bulk modulus is B0 = 344.0 GPa, with an elastic pressure derivative value of B0' = 4.08, matching experimental diamond anvil cell measurements within a 1.2% margin. The single-crystal elastic constants (C11, C33, C44, C12, and C13) increase monotonically under uniform compression, satisfying all Born mechanical stability parameters across the entire pressure range. The directional compressibility paths reveal that the crystal c-axis displays exceptional stiffness due to short, covalent rhenium-boron bonds. Electronic structure computations show a high density of states at the Fermi level, indicating that ReB² maintains its metallic profile under ultra-high pressures. These precise elastic records confirm the viability of transition metal borides as robust alternatives to conventional superhard diamond materials.
Keywords: Rhenium diboride; density functional theory; elastic constants; high pressure; structural stability; mechanical properties
Manuscript Timeline: Received: November 11, 2014; Revised: December 19, 2014; Accepted: January 08, 2015; Published: February 12, 2015
Citation: Morozov, V. I., & Gallagher, E. M. (2015). Elasticity Profiles and High-Pressure Phase Transitions in Ultra-Incompressible Rhenium Diboride. International Journal of Physics, 6(2), 9–16.
International Journal of Physics | Vol. 6, No. 1, January 2015 | pp. 1–8
DOI: 10.46882/2015/IJP/000057
Research Article
Title: Optical Soliton Dynamics and Wave Interactions in Cascaded Quadratic Nonlinear Waveguides
Names of Authors: L. K. Rousseau¹, N. K. Patel²
Authors’ Affiliations: ¹Laboratoire de Physique des Plasmas, École Polytechnique, Palaiseau, France; ²Department of Physics, Indian Institute of Technology, New Delhi, India
Abstract: Controlling ultra-short light pulses within integrated optical chips is essential for expanding the bandwidth of modern telecommunication networks. This study models optical soliton dynamics and characterizes multi-wave interactions within cascaded quadratic (chi^2) nonlinear waveguides. We solved the coupled non-linear Schrödinger equations governing the fundamental and second-harmonic fields using a variational method paired with split-step Fourier numerical simulations. The analytical framework derives the exact phase-matching conditions and power thresholds required to initiate stable multicolored solitary wave propagation. The results show that large phase mismatches generate a strong cascading effect, mimicking a cubic Kerr nonlinearity that stabilizes localized two-dimensional structures. The modulation instability growth rate was calculated as a function of mismatch parameters, revealing a maximum gain value of g = 3.12 cm^-1 under an input pulse intensity of 2.0 kW/cm². Increasing the mismatch parameter from 1.0 mm^-1 to 5.0 mm^-1 reduces the maximum instability gain by 54.0% and prevents pulse fragmentation. These findings provide strategies for controlling self-focusing in high-power laser systems and optimizing all-optical switching matrices.
Keywords: Nonlinear optics; optical solitons; quadratic nonlinearity; split-step Fourier method; modulation instability; phase matching
Manuscript Timeline: Received: October 05, 2014; Revised: November 22, 2014; Accepted: December 10, 2014; Published: January 14, 2015
Citation: Rousseau, L. K., & Patel, N. K. (2015). Optical Soliton Dynamics and Wave Interactions in Cascaded Quadratic Nonlinear Waveguides. International Journal of Physics, 6(1), 1–8.