Department of Physics
Permanent URI for this communityhttps://ir.nbu.ac.in/handle/123456789/4173
Physics is one of those departments with which North Bengal University started its journey in the year 1962. At present there are nine faculty members and ten non-teaching employees in the department. The department has active research groups in the field of (a) Liquid Crystal, (b) Relativity, Cosmology, and Astrophysics, (c) High-energy Heavy-ion Interaction and Cosmic-ray Physics, and (d) Solid-state devices. Several research projects sponsored by the DST, DAE, UGC, and Tea Research Board are running in the department. In the year 2003 the department received a financial support under the FIST programme from the DST, Govt. of India. The department offers both M.Sc. and Ph.D. courses. A semester system is followed in the M.Sc. level, with three different areas of specialization namely, Condensed Matter Physics, Electronics and Nuclear and Particle Physics, out of which a student can choose one. The annual intake capacity in M.Sc. is 40 students. In the Ph.D. programme of the department right now 25 research students are enrolled under the supervision of different faculty members. Almost all faculty members are involved in intra and inter-university national and international collaborations of scientific research. The department houses one IUCAA Resource Centre, a Data Centre for Observational Astronomy, six teaching laboratories, several research laboratories and one departmental library. From time to time the department organizes Seminars, Symposia, Conferences, Schools, Refresher Courses, and Outreach Programs.
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Item Open Access A Short Review on the Bosonization Duality in 2+1D Chern-Simons-Matter Theories(University of North Bengal, 2025-03) Dey, AnshumanThis review discusses Bose-Fermi dualities in 2+1 dimensional Chern-Simons-matter theories, focusing on the conjecture that free (regular) fermions coupled to a Chern-Simons gauge field are level-rank dual to Chern-Simons gauged critical (Wilson-Fisher) bosons. In the bosonic theory, the sign of the mass deformation determines whether the system enters a Higgsed (condensed) or unHiggsed (uncondensed) phase. We review large-N computations of the thermal free energy in both phases of the bosonic theory and explore how these results align with their fermionic counterparts under the proposed duality. Notably, this mapping reveals a striking feature : in the unHiggsed phase, the fermions are dual to fundamental scalar excitations, while in the Higgsed phase, the same fermionic degrees of freedom map onto massive W-bosons.Item Open Access A Brief overview of Nanomechanical Qubits(University of North Bengal, 2024-03) Samanta, ChandanQubits are the building blocks for quantum computers and quantum information processing. However, there is a great deal of dispute over the most ideal types of qubits. The nanomechanical qubit might be one potential addition to the qubit platforms. Here, we briefly outline the underlying physical principle of a nanomechanical qubit, where the mechanical vibrations stores the information.Item Open Access Calorimetric study of an induced nematic to smectic A phase transition in a binary system of two smectogens: Existence of double tricritical points(University of North Bengal, 2025-03) Parvin, Apsari; Das, Malay KumarIn this work, we investigate a series of binary mixtures comprising two smectogenic compounds, 5DBT (containing terminal group, NCS and exhibiting smectic A1 phase) and 10OCB (having terminal group, CN and exhibiting smectic Ad phase). The binary system exhibits an induced N (nematic) phase within a definite concentration limit between X5DBT = 0.05 and X5DBT = 0.95. Utilizing high-resolution MDSC setup, we have carried out a detailed heat capacity measurement at the induced N to smectic A (SmA) transition. Analysis of the latent heat confirms the occurrence of two tricritical points: one having the McMillan ratio = 0.981 and the other corresponding to 0.983. A distinct pretransitional heat capacity change close to the transition temperature is observed. The renormalization group theory involving a correction-to-scaling factor, effectively describes this anomaly. The critical exponent α follows a distinct pattern when plotted against both mole fraction (X5DBT ) and McMillan ratio (TNA/TIN). As the system approaches the tricritical point (TCP), a consistent shift from 2nd order to 1st order N–SmA transition is noticed on each end of the phase diagram. Both the TCP shares a common McMillan ratio = 0.982. Additionally, the 3D–XY model is precisely attained near X5DBT = 0.687, corresponding to TNA/TIN = 0.909.Item Open Access Design and Development of Mixed Perovskite Solar Cells with High Efficiency and Stability through DFT and AI-Based Design Approaches(University of North Bengal, 2025-03) Chatterjee, Suman; Subba, Subham; Talukdar, Avijit; Debnath, Pratik; Sarkar, JoyCompared to different solar technologies, Perovskite-based solar cells are preferred by many for their high PCE and cost-effectiveness. Still, building a market-ready solution requires handling various important issues related to stability, how the device is designed, and efficiency. The study presents comprehensive approaches involving Density Functional Theory (DFT), device modeling, and Machine Learning (ML) to improve and evaluate mixed perovskite materials. DFT was utilized to study the electronic structure, energy gap, and defect properties of perovskites. By using SCAPS-1D simulations, different optimization factors were studied. Furthermore, different ML algorithms were trained to find key device properties. The training involved both experiments and simulations to learn from the data and predict how each material would work, allowing for fast screening of various perovskite compositions. Because of this framework, researchers can identify new, efficient materials and learn more about how different compositions affect solar cell performance. This strategy uses DFT modeling, numerical simulation, and data analysis together to improve the speed of developing better perovskite solar cells.Item Open Access Effect of Core and Its Position on the Properties of Fluorinated Nematic Liquid Crystals(University of North Bengal, 2025-03) Singha, Biplab Kumar; Debnath, Ashim; Haldar, SripadaFive nematic liquid crystal (NLC) compounds have been investigated by polarizing optical microscopy (POM), molecular mechanics and dielectric spectroscopy. Introduction of ethane (– CH2CH2–) bridge, its position, surrounding rings and fluorination were found to influence considerably molecular dipole moment (μ), inclination (β) i.e., frame of reference, dielectric anisotropy (Δε), threshold voltage (Vth), splay elastic constant (K11), relaxation time (τ ) and activation energy (Ea). It is observed that compounds show very lower melting and clearing temperatures. Nematic (N) phase stability is also found to be broader. All compounds show super cooling property near to room temperature except compound 3o2pp-f (N1). Splay elastic constant (K11), an important parameter is found to vary from 10−11 N to 10−10 N. Comparatively lower value of K11, lower value of restoring torque and alternatively faster response can be achieved. Undesirable energy absorption is found in between few hundred kHz to MHz region i.e flip-flop in nature.Item Open Access Estimating Mass and Luminosity of Spectroscopic Binary Stars Using a Python-Based Computational Approach(University of North Bengal, 2025-03) Kundu, Jayashree; Mandal, Rakesh Kumar; Sarkar, TamalSpectroscopic binary stars provide crucial insights into stellar masses, orbital dynamics, and evolutionary processes. This study presents a computational approach to analyzing spectroscopic binary systems using Python by developing an algorithm to estimate their mass and luminosity. In our study, the algorithm processes the spectral data, particularly variations in the Hydrogen-alpha line over time (in Modified Julian Date), to compute radial velocities by incorporating Doppler shifts and applying barycentric corrections. A sinusoidal function is then fitted to the velocity variations to determine the orbital period. The stellar masses are derived using the radial velocity curve with the inclination angle and orbital parameters. Given the mass-luminosity relation, the luminosities of the stars are estimated. Since the derived mass of the system ranges between 2 and 55 times the mass of the sun, the luminosity can be calculated based on the mass-luminosity relation, where luminosity is proportional to the stellar mass raised to the power of 3.5. This computational method offers an efficient and accurate technique for studying spectroscopic binaries, which can be extended to analyze large datasets from astronomical surveys, enhancing our understanding of binary star evolution.Item Open Access The Exactly Solvable Poschl-Teller Potential(University of North Bengal, 2024-03) Dutta, ParikshitWe revisit a well known quantum mechanical problem, the trigonometric Pöschl-Teller potential, which is an exactly solvable one-dimensional problem. The potential appears in many physical systems of study and thus the technique of solution is interesting and important for students and readers to know. We wish to elaborate on this in this article.Item Open Access Exploring AC Conductivity and Microstructure of Iron-Vanadium Doped Systems(University of North Bengal, 2025-03) Ghosh, Jiban; Bhattacharya, SanjibThe present work focuses on the impact of partial substitution of ZnO (former) by various other oxides in the microstructure and AC conductivity of newly developed amorphous semiconducting systems containing two transition metal ions such as vanadium and iron. The current materials may be significantly helpful in specialized applications like high-power lasers for their high refractive indices. An insightful study of the composition-dependent microstructure and electrical transport behavior with various former-modifier ratios is of great interest, not only from an application perspective but also for academic purposes.Item Open Access Flexible Piezoelectric Energy Harvester Based on UV Light Emitting Ce3+-Complex-P(VDF-HFP) Composite Films(University of North Bengal, 2024-03) Barman, Priti Sundar; Adhikary, PrakritiIn this study, we report on the preparation of a polymer composite film with enhanced (_ 99%) electroactive phases _- and -phase) based on P(VDF-HFP) copolymer and Ce3+-complex. Furthermore, its utilization in piezoelectric-based flexible energy harvesting (PFEH) device fabrication has been studied, where the electrostatic interactions between the surface charges of Ce3+-complex and -CH2-/-CF2- molecular dipoles of P(VDF-HFP) via H-bonding co-operate to stabilize the electroactive phases and enhance its piezoelectric properties. PFEH generates _ 3 V of open circuit voltage and 0.16 _A short-circuit current under the external pressure impacting amplitude of 14.20 kPa. Moreover, it can successfully charge up capacitor by repeating finger impact which indicates its potency as an efficient energy-harvesting device. Besides this, the composite film exhibits an intense photoluminescence in the UV-region that might be very promising in the area of high-performance, energy-saving, flexible, solid-state UV light emitters and fabrication of hybrid multifunctional energy harvester where mechano-luminescence phenomenon might be possible to include.Item Open Access High-energy heavy-ion collision and quark-gluon plasma(University of North Bengal, 2025-03) Mali, Provash; Sarkar, Soumya; Mukhopadhyay, AmitabhaSome basic aspects of quark-gluon plasma and relativistic nuclear collisions are reviewed. General features of heavy-ion collisions like their space-time evolution, the thermodynamics and hydrodynamics of the intermediate fireball created therein, the phase diagram of QCD matter, the signatures of QGP formation etc., are summarily discussed. We expect that this introductory review will be able to draw a general interest among the graduate students to a very exciting area of physics.Item Open Access A Method of estimating the EAS cores of Monte Carlo showers for the GRAPES-3 experiment(University of North Bengal, 2024-03) Basak, AnimeshThe procedure of estimating the different extensive air shower (EAS) parameters is inherently linked to the accurate estimation of the cosmic-ray EAS cores. In EAS data analyses, the core of an EAS is estimated simultaneously with other crucial EAS parameters like shower size, shower age, etc. by fitting the lateral density data (LDD) of either the EAS charged secondaries or purely electrons with some suitably chosen lateral density function employing the maximum likelihood method. The present analysis estimates EAS cores using the LDD of electrons that fall on the scattered array detectors from the simulated EASs initiated by proton and iron primaries. Considering a densely packed detector array, including configurations akin to GRAPES-3, the research employs a straightforward weight average method (WAM) for the EAS core estimation. The findings reveal that around 95.5% of simulated showers exhibit EAS cores within a deviation range of approximately 1 m to 3 m from the actual cores of the CORSIKA Monte Carlo showers initiated by proton and iron primaries.Item Open Access Na2O Doped Solid State Battery Electrolytes: Preparation and Electrical Characterization(University of North Bengal, 2024-03) Ram, Rakesh; Bhattacharya, SanjibPresent work explores the development of Na2O doped electrolytes and their conduction behavior. Electrical transport behavior (mixed conduction) of as-developed electrolytes has been investigated with respect to frequency and temperature. A nature of flat conductivity in the lower frequency window may be caused due to diffusional motion of Na+. It is also noted that the conductivity shows dispersion near the high frequency regime. Electrical conductivity has also been analyzed with respect to temperature to explore their thermally activated nature. A little bit of difference in trajectories of current-voltage characteristics in both directions should make sense for their applications in the sectors of battery-electrolytes.Item Open Access On maximum compactness bound in relativistic theory(University of North Bengal, 2025-03) Sharma, RanjanThis article reviews recent developments in estimating the maximum compactness bound of a compact star in the General Theory of Relativity and some extended theories of gravity.Item Open Access Phase plane of a non-canonical scalar field model and cosmological consequences(University of North Bengal, 2025-03) Bhattacharya, Agnidipto; Biswas, Sujay Kr.This work deals with an investigation of phase plane analysis for a non-canonical scalar field in the background dynamics of spatially flat, homogeneous and isotropic Friedmann-Robertson-Walker (FRW) universe. Here, gravity is nonminimally coupled to scalar field having a real scalar field potential explicitly depending on cosmic time ‘t’. Nonlinear field equations are reduced to an autonomous system of ordinary differential equations by the suitable choice of dynamical variables. From the analysis of critical points, we have found the future decelerating phase of evolution of the universe.Item Open Access Prediction of Cross Port Output in Electro-optic Mach-Zehnder interferometer Using Artificial Neural Network(University of North Bengal, 2024-03) Gayen, Dilip Kumar; Chattopadhyay, TanayArtificial neural networks are essential for the design and analysis of complex algorithms. We have designed a circuit with an electro-optic Mach-Zehnder interferometer (EOMZI) driven by a photodiode. The output from the EOMZI’s cross bar port is used. Then, we have developed a photonic artificial neuron based on this setup. The outputs are validated using MATLAB, and the Artificial neural networks successfully generate the sigmoid function corresponding to the EOMZI switch’s cross port.Item Open Access Recent Efforts Towards Understanding the Early Universe from a Fundamental Quantum Perspective(University of North Bengal, 2024-03) Modak, Sujoy K.The observable universe is fundamentally inhomogeneous and anisotropic. Quantum description of the generation of these inhomogeneities and anisotropies is ill-understood and unsatisfactory. After providing a brief account of the standard approach of the generation of the classical density perturbations starting from the quantum fluctuations of inflaton field, I critically review various assumptions which are crucial for the success of this description, and point out various shortcomings around it. I also discuss the basic ideas and recent works by using an alternative path to overcome those shortcomings which is motivated by the so-called Collapse Model interpretation of quantum mechanics. Inspired by these works, I argue the necessity of constructing a class of manifestly inhomogeneous and anisotropic quantum states after inflation and discuss my recent works which provide one such prescription of building such a state, called the Tvacuum, defined in the radiation dominated stage of the early universe.Item Open Access A short course on the Su-Schrieffer-Heeger model(University of North Bengal, 2024-03) Ghosh, Tarun KantiWe review various topological properties of a dimer Su-Schrieffer-Heeger tight-binding model. Exact analytical expressions of the energy spectrum and corresponding eigenstates for any choice of system parameters are provided. We discuss the system’s parity, time-reversal, and chiral symmetries. The system undergoes a topological phase transition while tuning the hopping parameters. The topological phase is associated with the presence of the boundary modes and establishes the bulk-boundary correspondence.Item Open Access Spectral variability in the orbital profiles of TeV Binary LSI + 61o 303 in X-Ray window using XMM - Newton Observations(University of North Bengal, 2024-03) Sarkar, TamalLSI + 61o 303 is a high-mass X-ray binary consisting of a low-mass [M (1 - 4)M o] compact object orbiting around an early type B0 Ve star along an eccentric e = 0:7 orbit. It along with LS5039 are the only two known gamma-ray binary detected in the TeV band. Despite extensive observations the nature of this source, particularly whether it is a pulsar or a black hole (microquasar) system, is not clear. The mechanisms that lead to the multi-wavelength behavior are also uncertain. Recent approach to the study of LSI + 61o 303 has been to focus on possible correlated variability. There was an early indication that there is a correlation between the X-ray and TeV emission at the time where the latter was measurable. In a more recent observation, however, such a feature has not been found. In this work, we study the spectral variability of LSI + 61o 303 using four observations between 2001 to 2007 of XMM - Newton available from NASA archive and examine the correlation between low energy range and high energy part.Item Open Access Spin and valley dependent transport in a biased dice lattice(University of North Bengal, 2024-03) Tamang, LakpaWe study the spin and valley-dependent transport in a spin-orbit coupled biased dice lattice. We find that the presence of a bias term and the spin-orbit interaction (SOI) give rise to the spin-split energy spectrum. The SOI couples the valley and the spin degrees of freedom, resulting in a spin and valley-resolved Berry curvature. We find a profound variation in the Berry curvature for different spin states around both valleys. The spin and valley Hall conductivities are calculated for various values of the bias term. We find the interplay between the bias term and SOI term leads to a quantum phase transition from a topological insulating phase to a trivial band insulating phase accompanied by the emergence of the valley Hall effect and the suppression of the spin Hall effect.Item Open Access Study of the mechanical properties of CdS2 and its enhanced optoelectronic performance under Mn doping: a first principles study(University of North Bengal, 2025-03) Thapa, Bhawana; Shankar, AmitUsing density functional theory, a first-principles calculation was conducted to investigate the optoelectronic and mechanical properties of CdS2. The material exhibits semiconductor behavior with an indirect band gap of 1.3 eV under the GGA approach, which increases to 2.4 eV with mBJ correction. The pristine sample displays ductile characteristics and ionic bonding among its constituent atoms. Substituting Mn at the Cd site reduces the energy band gap while enhancing the material’s optical response. The pure CdS2 demonstrates favorable optical properties, including significant optical absorption, which is further improved by Mn doping. These features make CdS2 a promising candidate for optoelectronic applications such as photovoltaic devices, light emitters, and detectors.