arXiv subjects

Debnarayan Jana

Publications and source records attributed to Debnarayan Jana.

At least 19 recordsLinked to original sources

arXiv2025

Quantum Spin Hall Effect and Su-Schrieffer-Heeger Model Implementation in Novel C3N-based Dumbbell Morphologies

Two-dimensional carbon nitride materials have been the center of attention for their diverse usage in energy harvesting, environmental remediation and nanoelectronic applications. A broad range of utilities with decent synthetic plausibility have made this family a sweet spot to dive into, whereas the underlying analytical aspects are yet to have prominence. Recently, using the machinaries of first principles, we reported a family of six different structures C3NX with a unique dumbbell-shaped morphology, functionalizing the recently synthesized monolayer of C3N. Here we have critically explored the non-trivial topological phases of the semimetallic Dumbbell C3NX sheets and nanoribbons. Spin-orbit coupling induced gap across the Fermi level, its subsequent tuning via an external electric field, portrayal of band inversion from the Berry curvature distribution and the evaluation of topological index using the Wannier charge center (WCC) firmly establishes the traces of topological footprint. The real space decimation scheme and Green function technique evaluate the underlying spectral information with corresponding transport characteristics. Fascinating features of these quasi-1D systems are observed utilizing the Su-Schrieffer-Heeger (SSH) model where different twisted phases reveal distinct topological signatures even in a low atomic mass system like DB C4N.

cond-mat.mes-hall↗

arXiv2025

Navigating the Evolution of Two-dimensional Carbon Nitride Research: Integrating Machine Learning into Conventional Approaches

Carbon nitride research has reached a promising point in today's research endeavours with diverse applications including photocatalysis, energy storage, and sensing due to their unique electronic and structural properties. Recent advances in machine learning (ML) have opened new avenues for exploring and optimizing the potential of these materials. This study presents a comprehensive review of the integration of ML techniques in carbon nitride research with an introduction to CN classifications and recent advancements. We discuss the methodologies employed, such as supervised learning, unsupervised learning, and reinforcement learning, in predicting material properties, optimizing synthesis conditions, and enhancing performance metrics. Key findings indicate that ML algorithms can significantly reduce experimental trial-and-error, accelerate discovery processes, and provide deeper insights into the structure-property relationships of carbon nitride. The synergistic effect of combining ML with traditional experimental approaches is highlighted, showcasing studies where ML driven models have successfully predicted novel carbon nitride compositions with enhanced functional properties. Future directions in this field are also proposed, emphasizing the need for high-quality datasets, advanced ML models, and interdisciplinary collaborations to fully realize the potential of carbon nitride materials in next-generation technologies.

cond-mat.mtrl-sci↗

arXiv2022

One-Step Hydrothermal Synthesis of Sb 2 WO 6 Nanoparticle towards Excellent LED Light Driven Photocatalytic Dye Degradation

Pristine Antimony tungstate nanoparticles prepared via a simple hydrothermal process showcase interesting photocatalytic efficiency, degrading Methylene Blue (MB) completely in 180 min under visible light. In this study, the impact on crystalline quality and related optical properties as well as photocatalytic efficiency of antimony tungstate due to temperature variation during hydrothermal synthesis are explored. While X-ray diffraction (XRD) shows the polycrystalline nature of all synthesized samples, however a systematic increase in crystallite size is revealed by analysing the XRD peak broadening. XRD spectra are further examined by Rietveld analysis showing a change in unit cell volume. Additionally, the overall changes in the corresponding grain size and micro-strain developed in the crystals are determined using the Williamson-Hall plot. Moreover, significant variations in few Raman modes are observed with increasing synthesis temperature. A notable modification in the optical band gap as determined from the absorbance of the UV-Vis spectra is perceived with the change in synthesis temperature within the range of ~2.38-2.57 eV. Further, the photoluminescence measurement indicates that the synthesized antimony tungstate is weak luminescent material with a band-to-band emission at ~468 nm. Finally, photocatalytic efficiencies of the samples are ascertained to change with the synthesis parameter, estimated by decomposing methylene blue (MB), highest degradation rate constant (k) value is observed as 0.015 min -1 for the sample prepared at 180 o C. While the sample with the highest efficiency is also applied for degrading the Rhodamine B (RhB) and Potassium Dichromate (K 2 Cr 2 O 7 ) under visible light irradiation.

cond-mat.mtrl-sci↗

arXiv2021

Nitrogenated CQD decorated ZnO nanorods towards rapid photodegradation of rhodamine B: a combined experimental and theoretical approach

In this work, hybridization of nonmetal nitrogen-doped carbon dots (NCQDs) with ZnO nanorods (NRs) is utilized towards better photocatalytic degradation of rhodamine B under ultraviolet (UV) irradiation. The structural characterization is confirmed by XRD, XPS, FTIR and HRTEM measurements, while, optical properties have been investigated using UV-visible absorbance spectroscopy and photoluminescence study. The dye degradation using ZnO NR is recorded as ~69%, while the performance of ZnO/NCQD climbs up to ~90%, after nine minutes of UV irradiation. Furthermore, the reusability test suggests better stability of ZnO/NCQD than bare ZnO under photocorrosion. The cyclic voltammetry study confirms that the photoinduced electron-hole pairs originate from the heterojunction established between the interfaces of NCQD and ZnO. An insight on the photocatalytic excellence of ZnO/NCQD system is drawn from the density functional theory study. This indicates that appropriate band alignment of the heterostructure constituents is the key factor in this experimental attempt towards environment remedy.

cond-mat.mtrl-sci↗

arXiv2021

Combined theoretical and experimental study of the electronic and optical property of Sb$_2$WO$_6$

Both theoretical and experimental analysis are carried out to understand the physical properties of the fascinating electronic and optical properties of antimony tungstate (Sb$_2$WO$_6$). The nanosized ($\sim 40-80~nm$) material is produced using hydrothermal method followed by the SEM and XRD analysis to find the structural properties. The present calculations using PBEsol and PBE approximations for exchange-correlation potential are compared with the experimental structural parameters and in the case of the calculations using PBEsol approach the predicted crystal parameters and simulated XRD pattern are in excellent agreement with experimental results. The experimental absorption spectra measured in the ultraviolet-visible range give the bandgap of $2.42 ~eV$, while the most intense peak of photoluminescence spectra is found at $468nm~(2.65 ~eV)$. Using density functional theory (DFT) technique, the band structure and density of states for \swo~ are calculated and the calculated bandgap of $2.62 ~eV$ is in agreement with the experimental finding. From theoretical partial density of states calculations we identify that the bandgap is formed between the O$-2p_y$ orbitals bonded with Sb at valence band maxima and the W$-5d_{x^2-y^2}$ orbital at conduction band minima. The atomic level transitions responsible for the peaks of absorption spectra and photoluminescence spectra are identified as well by the means of DFT calculations. Following the matching of theoretical and experimental observations, the calculations of optical properties reveal the plasma frequency to be equal to $13.36 ~eV$.

cond-mat.mtrl-sci↗

arXiv2020

Semiconductor Physics: A Density Functional Journey

The journey of theoretical study on semiconductors is reviewed in a non-conventional way. We have started with the basic introduction of Hartree-Fock method and introduce the fundamentals of Density Functional Theory (DFT). From the oldest Local Density Approximations (LDA) to the most recent developments of semi-local corrections [Generalised Gradient Approximation (GGA), Meta-GGAs], hybrid functionals and orbital dependent methodologies are discussed in detail. To showcase the performance of DFT, results obtained via different approximations are compared. We indicate the success of semi-local approximations in structural properties prediction. We also show how less computationally costly but withstand architecture of some semi-local DFT methods can solve the long riddle of bandgap underestimation. In semiconductor physics, the importance of not only the band structure prediction, but also, the proper calculation of Fermi energy, and, exact finding of band alignment is argued. The comparison of Fermi energy dependent properties can channelize the theoretical studies on modern age environment-friendly researches on semiconductors, like artificial photocatalysis, energy efficient opto-electronic devices, etc. This prescription on proper choice of DFT method is potentially competent to complement the experimental findings as well as can open up a pathway of advanced semiconducting materials discoveries.

cond-mat.mtrl-sci↗

arXiv2020

Electronic structural critique of interesting thermal and optical properties of C$_{17}$Ge germagraphene

In this communication, we report a theoretical attempt to understand the involvement of electronic structure in determination of optical and thermal properties of C$_{17}$Ge germagraphene, a buckled two dimensional material. The structure is found to be a direct bandgap semiconductor with low carrier effective mass. Our study has revealed that the effect of spin-orbit coupling on the band structure and in appearance of spin Hall current in the material. A selectively high blue to ultraviolet light absorption and a refractive index comparable to flint glass open up the possible applicability of this material for optoelectronic devices. From electronic structural point of view, we investigate the reason behind its moderately high Seebeck coefficient and power factor comparable to traditional thermoelectric materials. Besides its narrow bandgap, relatively smaller work function of C$_{17}$Ge ($4.361 ~eV$) than graphene ($4.390 ~eV$) and germanene ($4.682 ~eV$) assures more easily removal of electron from the surface. This material is turned out to be an excellent alternative for futuristic semiconductor application from optical to thermal device regime.

cond-mat.mtrl-sci↗

arXiv2019

Exploring the role of electronic structure on photo-catalytic behavior of carbon-nitride polymorphs

A fully self-consistent density-functional theory (DFT) with improved functionals is used to provide a comprehensive account of structural, electronic, and optical properties of C$_{3}$N$_{4}$ polymorphs. Using our recently developed van Leeuwen-Baerends (vLB) corrected local-density approximation (LDA), we implemented LDA+vLB within full-potential N$^{th}$-order muffin-tin orbital (FP-NMTO) method and show that it improves structural properties and band gaps compared to semi-local functionals (LDA/GGA). We demonstrate that the LDA+vLB predicts band-structure and work-function for well-studied 2D-graphene and bulk-Si in very good agreement with experiments, and more exact hybrid functional (HSE) calculations as implemented in the Quantum-Espresso (QE) package. The structural and electronic-structure (band gap) properties of C$_{3}$N$_{4}$ polymorphs calculated using FP-NMTO-LDA+vLB is compared with more sophisticated hybrid-functional calculations. We also perform detailed investigation of photocatalytic behavior using QE-HSE method of C$_{3}$N$_{4}$ polymorphs through work-function, band (valence and conduction) position with respect to water reduction and oxidation potential. Our results show $\gamma$-C$_{3}$N$_{4}$ as the best candidate for photocatalysis among all the C$_{3}$N$_{4}$~polymorphs but it is dynamically unstable at `zero' pressure. We show that $\gamma$-C$_{3}$N$_{4}$ can be stabilized under hydrostatic-pressure, which improves its photocatalytic behavior relative to water reduction and oxidation potentials.

cond-mat.mtrl-sci↗

arXiv2019

Simple correction to bandgap in IV and III-V semiconductors: an improved first-principles local density functional theory

We report results from a fast, efficient, and first-principles full-potential N$^{th}$-order muffin-tin orbital (FP-NMTO) method combined with van Leeuwen-Baerends correction to local density exchange-correlation potential. We show that more complete and compact basis set is critical in improving the electronic and structural properties. We exemplify the self-consistent FP-NMTO calculations on group IV and III-V semiconductors. Notably, predicted bandgaps, lattice constants, and bulk moduli are in good agreement with experiments (e.g., we find for Ge $0.86~e$V, $5.57$~Å, $75$~GPa vs. measured $0.74~e$V, $5.66$~Å, $77.2$~GPa). We also showcase its application to the electronic properties of 2-dimensional $h-$BN and $h-$SiC, again finding good agreement with experiments.

cond-mat.mtrl-sci↗

arXiv2019

Electronic and optical properties of Germagraphene, a direct band-gap semiconductor

In this communication, we report a theoretical attempt to understand the electronic and optical properties of germagraphene, a two-dimensional graphene analogue. We study two different structures, C$_{17}$Ge and C$_{16}$Ge. In the C$_{17}$Ge structure, a germanium atom replaces a carbon atom while in C$_{16}$Ge structure, a carbon-carbon bond is replaced by a single germanium atom. These two types of doping have been experimentally made possible by Tripathi \etal [{\it{ACS Nano (2018) 1254641-4647}}]. We find that C$_{16}$Ge has a planar structure, whereas, the Ge atom in C$_{17}$Ge settles in an out-of-the plane position, resulting in a buckled structure. Due to Ge doping, the band-gaps open up in both. The 1.227 eV direct gap of C$_{17}$Ge is ideal for effective light absorbance and optoelectronic devices. Further study of optical properties supports this claim as well.

physics.comp-ph↗

arXiv2015

Configuration and Self-averaging in disordered systems

The main aim of this work is to present two different methodologies for configuration averaging in disordered systems. The Recursion method is suitable for the calculation of spatial or self-averaging, while the Augmented space formalism averages over different possible configurations of the system. We have applied these techniques to a simple example and compared their results. Based on these, we have reexamined the concept of spatial ergodicity in disordered systems. The specific aspect, we have focused on, is the question "Why does an experimentalist often obtain the averaged result on a single sample ?" We have found that in our example of disordered graphene, the two lead to the same result within the error limits of the two methods.

cond-mat.mtrl-sci↗

arXiv2014

A real-space study of random extended defects in solids : application to disordered Stone-Wales defects in graphene

We propose here a first-principles, parameter free, real space method for the study of disordered extended defects in solids. We shall illustrate the power of the technique with an application to graphene sheets with randomly placed Stone-Wales defects and shall examine the signature of such random defects on the density of states as a function of their concentration. The technique is general enough to be applied to a whole class of systems with lattice translational symmetry broken not only locally but by extended defects and defect clusters. The real space approach will allow us to distinguish signatures of specific defects and defect clusters.

cond-mat.mtrl-sci↗

arXiv2013

A complete theory for the magnetism of an ideal gas of electrons

We have explored Pauli paramagnetism, Landau diamagnetism and de Haas-van Alphen effect in a single framework, and unified these three effects for all temperatures as well as for all strengths of magnetic field. Our result goes beyond Pauli-Landau result on the magnetism of the 3-D ideal gas of electrons, and is able to describe crossover of the de Haas-van Alphen oscillation to the saturation of magnetization. We also have obtained a novel asymptotic series expansion for the low temperature properties of the system.

cond-mat.stat-mech↗

arXiv2012

Thermodynamics of quantum gases for the entire range of temperature

We have analytically explored thermodynamics of free Bose and Fermi gases for the entire range of temperature, and have extended the same for harmonically trapped cases. We have obtained approximate chemical potentials of the quantum gases in closed forms of temperature so that the thermodynamic properties of the quantum gases become plausible specially in the intermediate regime between the classical and quantum limits.

cond-mat.quant-gas↗

arXiv2012

Excess energy of an ultracold Fermi gas in a trapped geometry

We have analytically explored finite size and interparticle interaction corrections to the average energy of a harmonically trapped Fermi gas below and above the Fermi temperature, and have obtained a better fitting for the excess energy reported by DeMarco and Jin [Science $\textbf{285}$, 1703 (1999)]. We have presented a perturbative calculation within a mean field approximation.

cond-mat.quant-gas↗

arXiv2009

Non-universal finite size scaling of rough surfaces

We demonstrate the non-universal behavior of finite size scaling in (1+1) dimension of a nonlinear discrete growth model involving extended particles in generalized point of view. In particular, we show the violation of the universal nature of the scaling function corresponding to the height fluctuation in (1+1) dimension. The 2nd order moment of the height fluctuation shows three distinct crossover regions separated by two crossover time scales namely, tx1 and tx2. Each regime has different scaling property. The overall scaling behavior is postulated with a new scaling relation represented as the linear sum of two scaling functions valid for each scaling regime. Besides, we notice the dependence of the roughness exponents on the finite size of the system. The roughness exponents corresponding to the rough surface is compared with the growth rate or the velocity of the surface.

cond-mat.stat-mech↗

arXiv1996

Charged Scalar Field in an external magnetic Field: Renormalisation and Universal Diamagnetism

The physical and mathematical mechanism behind diamagnetism of N (finite) spinless bosons (relativistic or non-relativistic) is well known. The mathematical signature of this diamagnetism follows from Kato's inequality while its physical way of understanding goes back to Van Leewen. One can guess that it might be true in the field theoretic case also. While the work on systems with a finite number of degrees of freedom suggests that the same result is true in a field theory, it does not by any means prove it. In the field theoretic context one has to develop a suitable regularisation scheme to renormalise the free energy. We show that charged scalar fields in (2+1) and (3+1) dimensions are always diamagnetic, even in the presence of interactions and at finite temperatures. This generalises earlier work on the diamagnetism of charged spinless bosons to the case of infinite degrees of freedom. We also discuss possible applications of the theory.

cond-mat↗

arXiv1995

Imbibition: An Example of Nonconserved Cellular Automaton

We report an imbibition experiment in 2D random porous media in which height - height correlation function grows with a nonuniversal exponent. We find the exponent to depend on evaporation. A cellular automaton model for imbibition based on first principles is presented. A numerical study of the model gives results which are consistent with the experiment. The interface is shown to exhibit self-organised criticality (SOC).

cond-mat↗