arXiv subjects

Muhammad Anisuzzaman Talukder

Publications and source records attributed to Muhammad Anisuzzaman Talukder.

11 recordsLinked to original sources

arXiv2026

Tailoring the Frequency-Dependent Optical Response of Hematite through Mono- and Co-Doping: A First-Principles Study

Understanding the effects of doping on the crystal structure and optical properties of semiconductor materials is crucial for advancing next-generation semiconductor and photonic technologies. Although various studies have focused on doped hematite ($\alpha$-Fe$_2$O$_3$), the relationship between dynamical stability and optical properties remains insufficiently explored. This study presents a comprehensive first-principles investigation that simultaneously evaluates the phonon dispersion characteristics and frequency-dependent optical response of B-doped, Y-doped, and (B, Y)-co-doped $\alpha$-Fe$_2$O$_3$, providing deeper insights into the underlying mechanisms. We examined the finite-temperature vibrational properties, dielectric function, and optical characteristics to comprehend the lattice dynamics and light-matter interactions under electromagnetic radiation. Vibrational thermodynamics reveal that pristine and Y-doped hematite maintain dynamic stability, while B-doped hematite exhibits imaginary phonon modes indicating lattice instability due to distortions in the Fe--O framework. Notably, Y co-doping with B helps suppress these soft modes, restoring structural stability through lattice relaxation and improved interatomic forces. B doping enhances low-energy absorption by introducing additional states in the valence band, while Y doping alters orbital hybridization, leading to a broader dispersion. In the optical regime, doped hematite displays dominant interband transitions below $2$ eV and strong absorption between 1.80 eV and 4 eV. The (B, Y) co-doping combines the low-energy benefits with an improved optical response profile. In summary, doping significantly enhances lattice vibrations, light-matter interactions, and optical responses, providing an effective strategy for tailoring hematite for diverse applications in photoactive, optoelectronic, and photonic technologies.

cond-mat.mtrl-sci↗

arXiv2026

Mechanistic Insights into Enhanced Alkaline Oxygen Evolution on Zn-Al Alloy Electrodes

Electrochemical water electrolysis, which produces clean energy carriers to mitigate carbon emissions, lacks suitable, low-cost electrodes for efficient oxygen evolution reaction (OER) in alkaline water splitting. To address this challenge, we developed Zn-Al alloy electrodes with varying Al contents up to 20 wt.% via powder metallurgy method and conducted electrochemical measurements of the OER in alkaline solution to investigate their catalytic performance. We also performed first-principles calculations to examine their thermodynamic phase stability and electronic structures. Both theoretical and experimental results indicated that incorporating $\geq 20$ wt.% Al into Zn led to thermodynamic phase instability and secondary-phase segregation in Al-rich regions, limiting reaction kinetics and reducing catalytic efficiency. Although the Al content of 5 wt.% into Zn exhibited favorable thermodynamic and electronic characteristics, but its electrochemical performance was inefficient and poor due to inadequate reaction active sites on the surface. In contrast, the 10 wt.% and 15 wt.% Al into Zn showed approximately three- and two-fold increases in anodic exchange current density relative to pure Zn, respectively. Additionally, the anodic overpotential losses ($\eta_{0,a}$) measured at a current density of 12 mAcm$^{-2}$ were 0.240 V for Zn$_{0.9}$Al$_{0.1}$ and 0.5603 V for Zn$_{0.85}$Al$_{0.15}$, significantly lower than that of pure Zn ($\eta_{0,a} = 1.086$ V). While Zn$_{0.9}$Al$_{0.1}$ and Zn$_{0.85}$Al$_{0.15}$ showed similar charge transfer resistance ($R_{\rm CT}$), Zn$_{0.9}$Al$_{0.1}$ demonstrated superior reaction kinetics and lower $\eta_{0,a}$ across all samples tested. Furthermore, the improved kinetics and reduced overpotential of the Zn-Al alloys favorably compare with those of other transition-metal-based catalysts, including Fe-Co-Ni-Mo alloys and Fe-doped CuO.

cond-mat.mtrl-sci↗

arXiv2026

Voltage-controlled beam steering in liquid-crystal-integrated dual-mode plasmonic nanolaser

Dynamic control of laser emission direction is crucial for developing compact and reconfigurable nanophotonic devices. In this work, we numerically present a plasmonic nanolaser (PNL) integrated with a voltage-controlled liquid crystal (LC) layer to achieve active beam steering. We modeled the orientation of LC molecules under an applied bias and incorporated this into electromagnetic simulations to assess the optical response. We observed lasing at an emission wavelength of 870 nm for the single-mode PNL, with discrete voltage-dependent deflections of the far-field emission of up to $\pm67$\textdegree, while maintaining a beam divergence of less than 1\textdegree. The steering characteristics were significantly influenced by the electro-optic properties of the LC layer, with an optimized thickness of 3 $\mu$m. The structural periodicity governed the achievable angular separation and emission stability. Furthermore, we extended the concept to a dual-mode nanolaser based on a merged nanohole array (NHA), which supports two lasing wavelengths at 873 nm and 880 nm. Both lasing modes exhibited simultaneous voltage-dependent angular tuning without altering the cavity geometry. These results highlight the potential of LC-integrated PNLs as voltage-controlled, reconfigurable light sources for applications in optical interconnects, beam routing, adaptive imaging, and multiplexed communication.

physics.optics↗

arXiv2026

Effects of Edge Atoms and Channel Width on Charge Storage in Nanoporous Carbon Supercapacitors

The amorphous structure of nanoporous carbon electrodes in supercapacitors complicates the establishment of clear links between electrode geometry and capacitance. In this work, we examine how specific structural features govern charge storage and explain capacitance variations among carbide-derived carbon (CDC) electrodes. Two key methodological and mechanistic advances are introduced. First, we propose a physically motivated, electric-field-based definition of the ion sphere of influence, which avoids the ambiguity of radial distribution function-based cutoffs and enables a more reliable characterization of local ion--electrode interactions. Second, we introduce an ion-resolved channel-width descriptor that quantifies pore accessibility by identifying the narrowest passage a counter-ion must traverse to enter a pore, directly linking accessibility to ion decoordination. Using atomistic molecular dynamics simulations of supercapacitors comprising realistic CDC electrodes and a room-temperature ionic liquid electrolyte under applied potentials, we show that carbon atoms located at the edges of graphitic sheets consistently accumulate higher charge than basal-plane atoms across all electrode types. The fraction of edge atoms increases with structural disorder and correlates with enhanced capacitance, in agreement with recent experimental findings linking disorder to charge storage. Furthermore, analysis of pore size and channel width reveals that ion decoordination is governed primarily by channel width rather than pore size alone. Together, these results establish edge atom concentration and pore channel width as decisive structural descriptors controlling charge accumulation in nanoporous carbon supercapacitors, providing clear design guidelines for optimizing electrode architectures.

physics.chem-ph↗

arXiv2025

Re-Engineering Hematite: Synergistic Co-Doping Routes to Efficient Solar Water Splitting

Solar-driven water electrolysis requires high-performance photoelectrodes that exhibit excellent photoabsorption, superior charge transport, and optimized thermal management. In this work, we conducted a first-principles investigation to explore optimized doping conditions for hematite ($\alpha$-Fe$_2$O$_3$) by incorporating boron (B), yttrium (Y), and niobium (Nb) mono-dopants, as well as (B, Y) and (B, Nb) co-dopants. To identify the optimal dopant elements and concentrations, we evaluated electronic charge transport, thermal properties, and magnetic susceptibility over a temperature ($T$) range of 300 to 900 K and doping densities ($N$) from $10^{19}$ to $10^{21}$ cm$^{-3}$. The B-doped, (B, Y)-doped, and (B, Nb)-doped $\alpha$-Fe$_2$O$_3$ photoelectrodes showed significantly reduced band gap energy ($E_g$) relative to $\alpha$-Fe$_2$O$_3$. In comparison, Y and Nb dopants only slightly reduced $E_g$ relative to $\alpha$-Fe$_2$O$_3$. While B doping introduced impurity states near the Fermi level that limited thermoelectric charge transport, $\alpha$-Fe$_2$O$_3$ photoelectrodes doped by other elements exhibited notable improvements, including enhanced visible-light absorption, increased carrier concentration, improved electrical conductivity ($\sigma$), and efficient thermal management. Additionally, these doped photoelectrodes exhibited a remarkable increase in Pauli magnetic susceptibility ($\chi$) by two orders of magnitude compared to pristine $\alpha$-Fe$_2$O$_3$, indicating exciting potential for generating spin-selective polarized currents. Overall, our findings revealed that the co-doping conditions are the most effective for enhancing the performance of $\alpha$-Fe$_2$O$_3$, providing a low-cost and high-efficiency solution for sustainable green hydrogen (H$_2$) generation in photocatalytic water splitting.

physics.chem-ph↗

arXiv2025

Physics-Informed Electrochemical Model of Cathodic Corrosion in Alkaline Media

Electrochemical corrosion significantly reduces the durability of electrodes in water electrolyzers, adversely affecting hydrogen (H$_2$) production and cell efficiency. Current theoretical models inadequately assess corrosion behaviors in alkaline water electrolyzers. To address this, we developed a physics-informed electrochemical corrosion model evaluating the corrosion characteristics of cathodes in alkaline systems, accounting for factors such as exchange current density ($J_0$), redox potential ($E_0$), Gibbs free energy of hydrogen adsorption ($\Delta G_{\rm H}$), electrolyte concentration ($C$), system pressure ($P$), and temperature ($T$). The model calculates metrics including corrosion potential ($E_{\rm corr}$), corrosion current density ($J_{\rm corr}$), and corrosion rate ($C_R$). Our findings from potentiodynamic polarization indicate that gold (Au) shows the highest durability, while copper (Cu) and nickel (Ni) are promising cost-effective alternatives. This work enhances the understanding of corrosion dynamics, contributing to the design of more efficient electrolyzer cells for hydrogen production.

physics.chem-ph↗

arXiv2025

Enhancing Electronic and Optical Properties of $\alpha$-Fe$_2$O$_3$ by Introducing B, Y, and Nb Dopants for Improved Photoelectrochemical Water Splitting

Advanced theoretical investigations are crucial for understanding the structural growth mechanisms, optoelectronic properties, and photocatalytic activity of photoelectrodes for efficient photoelectrochemical water splitting. In this work, we conducted first-principles calculations aimed at designing $\alpha$-Fe2O3 photoelectrodes incorporating mono-dopants such as boron (B), yttrium (Y), and niobium (Nb), as well as co-dopants (B, Y) and (B, Nb) to enhance the performance of photoelectrochemical cells. We assessed the thermodynamic phase stability by calculating formation enthalpy ($E_f$) and examining material properties, including microstrain ($\mu_\epsilon$) and crystallite size ($D$). The mono-dopants, Y and Nb, and the co-dopants, (B, Y) and (B, Nb), exhibited negative $E_f$ values under the substitutional doping method, confirming their thermodynamic phase stability and suggesting their practical viability for experimental implementation. Notably, the values of $\mu_\epsilon$ and $D$ fell within the ranges observed experimentally for $\alpha$-Fe2O3, indicating their effectiveness in growth mechanisms. To gain a comprehensive understanding of the optoelectronic properties of doped $\alpha$-Fe2O3, we calculated the electronic band structure, density of states, atom's ionic charge, and optical absorption coefficient. This analysis allowed us to examine the improvements in the electronic charge characteristics and photon-electron interactions. B-doped $\alpha$-Fe2O3 led to the formation of impurity bands, which were mitigated by utilizing co-dopants (B, Y) and (B, Nb). The metal dopants, Y and Nb, significantly increased the charge carrier density, while the co-dopants, (B, Y) and (B, Nb), substantially enhanced light absorption in the visible spectrum.

cond-mat.mtrl-sci↗

arXiv2025

Enhanced Hydrogen Evolution Using $\beta$-MnO$_2$ Monolayer on Ni Electrode with Engineered Oxygen Vacancies

Developing cost-effective and high-performance electrodes is critical for advancing hydrogen (H$_2$) production through electrochemical water splitting. In this study, we present a novel electrode design by depositing a $\beta$-MnO$_2$ monolayer on a conventional Ni(100) substrate (MnO$_2$(110)/Ni(100)) and systematically investigate its electrocatalytic properties. This work uniquely explores the influence of oxygen vacancies (OVs) at distinct sites -- Osub-top and bridge sites -- on both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Our findings reveal that the Osub-top vacancy (OOV-MnO$_2$(110)/Ni(100)) significantly enhances HER activity, achieving a hydrogen Gibbs free energy ($\Delta G_{\rm H}$) of $-0.015$ eV, which surpasses the performance of noble metals such as Pt/C ($-0.082$ eV) and Ir ($-0.08$ eV). Additionally, the cathodic exchange current density $(J_{0,c})$ of OOV-MnO$_2$(110)/Ni(100) reaches $10^{-0.774}$ Acm$^{-2}$, outperforming Pt/C ($10^{-0.92}$ Acm$^{-2}$) and Ir ($10^{-1.44}$ Acm$^{-2}$). Electrochemical analysis confirms a cathodic activation overpotential $(\eta_{a,c})$ of 0.141 V at 10 mAcm$^{-2}$ in a 0.5 M H$_2$SO$_4$ solution, achieving a hydrogen production rate (HPR) of 0.91 mmolh$^{-1}$cm$^{-2}$ at an applied voltage ($V_{\rm app}$) of 1.60 V. This study provides the first comprehensive analysis of site-specific oxygen vacancy effects on bifunctional MnO$_2$-based electrodes, demonstrating superior HER activity while maintaining dual functionality for both cathodic and anodic processes. Our results highlight the potential of engineered oxygen vacancies to develop low-cost, high-efficiency electrodes for sustainable hydrogen production, offering a competitive alternative to precious metal-based catalysts.

physics.chem-ph↗

arXiv2025

Time- and frequency-resolved dynamics of resonant two-photon terahertz quantum cascade lasers

Two-photon terahertz (THz) quantum cascade lasers (QCLs) can immensely improve the conventional applications of THz frequency sources and open windows to new applications due to their ability to generate quantum-entangled twin photon beams. The rich intrinsic non-linearity in a two-photon THz QCL arises from cascaded photon transitions, leading to time-resolved and frequency-resolved dynamics that are less predictable. This work investigates the time- and frequency-resolved dynamics of a resonant two-photon THz QCL by numerically solving the coupled Maxwell-Bloch equations. Our findings indicate that the output intensity is significantly higher, and the emission spectra are much broader in a two-photon THz QCL than in a conventional one-photon THz QCL. Additionally, a pronounced Risken-Nummedal-Graham-Haken (RNGH) instability onsets for a resonant two-photon QCL at a smaller pumping current. We also observe an increase in the number of lasing modes, as well as a higher power per line in a resonant two-photon QCL. Furthermore, Rabi splitting is observed in the emission spectra at high pumping currents.

physics.optics↗

arXiv2025

Three-dimensional imaging of biological cells using surface plasmon coupled emission

Biological cell imaging has become one of the most crucial research interests due to its wide-ranging applications in biomedical and microbiology studies. However, three-dimensional (3D) imaging of biological cells remains critically challenging and often requires prohibitively expensive and complex equipment. Therefore, a low-cost imaging technique with a simpler optical arrangement is highly desirable. We propose an approach to obtain accurate 3D cell images using surface plasmon coupled emission (SPCE) patterns from a fluorescently labeled biological cell, eliminating the need for conventional microscopes or extensive data processing. An imaging methodology has been developed and theoretically demonstrated to reconstruct 3D cell structures from detected SPCE patterns. The reconstructed 3D images closely match the actual cell geometries. The technique has been applied to both regular and irregular cell shapes. In each case, the root-mean-square error (RMSE) between the reconstructed images and the actual structures remains within a few percent. For a circular-shaped cell base, the RMSE is $\lesssim 1.4\%$, while for irregular cell bases, the RMSE is $\lesssim 2.8\%$. Finally, a 3D image of a random cellular structure is obtained with an RMSE of $\lesssim 6.5\%$. Despite being in its initial stages of development, the proposed technique demonstrates promising results considering its simplicity and low cost.

physics.optics↗

arXiv2023

Theoretical investigation of slow gain recovery of quantum cascade lasers observed in pump-probe experiment

Time-resolved spectroscopy-based pump-probe experiments performed on quantum cascade lasers (QCLs) exhibit an initial fast gain recovery followed by a slow tail such that the equilibrium gain is not recovered in a cavity round-trip time. This ultra-slow gain recovery or non-recovered gain cannot be explained by only the intersubband carrier dynamics of QCLs. This work shows that the Fabry-Perot cavity dynamics and localized intersubband electron heating of QCLs are essential in ultra-slow and nonrecovered gain recovery. We developed a comprehensive model, coupling cavity dynamics to the intersubband electrons' thermal evolution. We employ a four-level coupled Maxwell-Bloch model that considers temperature-dependent scattering and transport mechanisms in calculating the gain recovery dynamics. If an intense pump pulse electrically pumped close to the threshold propagates in the forward direction after being coupled into the cavity, the reflected pump pulse will significantly deplete the gain medium while propagating in the backward direction. Additionally, we show that the intersubband electron sustains a localized high temperature even after the pump pulse has left, which affects the overall carrier dynamics and leads to an ultra-slow gain recovery process. At near-perfect reflectivity, we observe a gain depletion of 4% for 2 mm QCL. We further demonstrate that an additional 10% gain depletion of probe pulse is seen at a steady state when the laser is pumped at 1.6 times the threshold compared to the case where the hot electron effect is not considered.

physics.optics↗