Asis. K. Bandyopadhyay

Bio: Asis. K. Bandyopadhyay is an academic researcher from Government College of Engineering and Ceramic Technology. The author has contributed to research in topics: Klein–Gordon equation & Transition metal. The author has an hindex of 2, co-authored 4 publications receiving 19 citations.

Fano resonance due to discrete breather in nonlinear Klein–Gordon lattice in metamaterials

Abstract: The richer variety of Klein–Gordon basis is already established for discrete breathers in metamatetrials. Based on this attempt, we show various anomalous Fano resonance behaviors that have been experimentally observed, but cannot be explained by nonlinear Schrodinger model. Certain material parameters of Klein–Gordon lattice in metamaterials are related for the first time with characteristics of Fano resonance, which can be utilized for beam filtering and for high-resolution biological sensing technology. Although relations with coupling and other parameters exist, the most remarkable relation is observed with linear permittivity that could control the wave transmission characteristics in metamaterials for applications in optical engineering.

Spin-exchange interaction between transition metals and metalloids in soft-ferromagnetic metallic glasses.

Abstract: High-performance magnetic materials have immense industrial and scientific importance in wide-ranging electronic, electromechanical, and medical device technologies. Metallic glasses with a fully amorphous structure are particularly suited for advanced soft-magnetic applications. However, fundamental scientific understanding is lacking for the spin-exchange interaction between metal and metalloid atoms, which typically constitute a metallic glass. Using an integrated experimental and molecular dynamics approach, we demonstrate the mechanism of electron interaction between transition metals and metalloids. Spin-exchange interactions were investigated for a Fe-Co metallic glass system of composition [(Co1-x Fe x )0.75B0.2Si0.05]96Cr4. The saturation magnetization increased with higher Fe concentration, but the trend significantly deviated from simple rule of mixtures. Ab initio molecular dynamics simulation was used to identify the ferromagnetic/anti-ferromagnetic interaction between the transition metals and metalloids. The overlapping band-structure and density of states represent 'Stoner type' magnetization for the amorphous alloys in contrast to 'Heisenberg type' in crystalline iron. The enhancement of magnetization by increasing iron was attributed to the interaction between Fe 3d and B 2p bands, which was further validated by valence-band study.

Domain Wall Width in Different Ferroelectrics via Perturbation Route

Abstract: The domains are of fundamental interest for engineering a ferroelectric material. The domain wall and its width control the ferroelectric behavior to a great extent. The stability of polarization in the context of Landau-Ginzburg free energy functional has been worked out in a previous work by a perturbation approach, where two limits of domain wall width were estimated within the stability zone and they were also found to correspond well with the data on lithium niobate and lithium tantalate. In the present work, it is shown that this model is valid for a wide range of ferroelectric materials and also for a given ferroelectric, such as lithium niobate with different levels of impurities, which are known to affect the domain wall width.

Effective Mass in Bose-Einstein Condensation in the Bound State and Phonon Propagation in the Unbound States

Abstract: The dark and bright solitons in different systems are already known in Klein-Gordon lattice. Instead of an external driving force, if the intrinsic field is only considered, then the modal dynamics for small oscillations could be characterized by the bound state in a limited range of frequency, revealed via associated Legendre polynomial. Bose Einstein condensation takes place around bosonic particles having different wave functions within the bound states in the temperature region T = 0 to Tc having implication for the effective mass of the system. The pairing and interplay between the dark and bright solitons also occur with their effect on the condensation. This effective mass is calculated via statistical mechanics route by two-part partition function that also gives an indication for the transition temperature. The disappearance of the bound state after a critical frequency, or equivalently, after a critical temperature, gives rise to quasi-particles or phonons in the unbound states that propagate through the domains.

A giant localized field enhancement and high sensitivity in an asymmetric ring by exhibiting Fano resonance

Abstract: The optical properties of asymmetric ring structures are investigated theoretically by using the discrete dipole approximation method. The numerical results revealed that this kind of structure can achieve a giant localized field enhancement (LFE, 264) and a high LSPR sensitivity (corresponding FOM, 8.28) in the visible spectrum by Fano resonance, whose origin is discussed based on plasmon hybridization theory. Furthermore, the dependence of the Fano resonance on the polarization states of the incident light is also demonstrated. Giant LFE and high LSPR sensitivity enable this structure to be promising for surface enhanced Raman spectroscopy and sensing applications.

Tunable Fano resonances of Lamb modes in a pillared metasurface

Abstract: In this work, Fano resonance is studied in a pillared acoustic metasurface, which originates from the avoided crossing of strongly coupled individual monopolar modes of two dissimilar pillars in one unit cell. The Fano resonance manifests itself as an out-of-phase compressional (monopolar) vibrations of the two pillars coupled through the plate. The Fano asymmetric transmission profile can be analyzed through the interference between the incident wave and the scattered wave emitted by resonant pillars. The peak in the asymmetric transmission is always maintained either the coupling of the two pillars is strong or weak. It is further found that the Fano resonance can be tuned by varying different geometrical parameters, such as the height/diameter of the pillars, the distance between the two pillars, or introducing an inner hole into the pillars which can possibly be filled with a liquid.

Fano resonances with discrete breathers

Abstract: A theoretical study of linear wave scattering by time-periodic spatially localized excitations (discrete breathers) is presented. A peculiar effect of total reflection occurs due to a Fano resonance when a localized state originating from closed channels resonates with the open channel. For the discrete nonlinear Schrödinger chain, we give an analytical result for the frequency dependence of the transmission coefficient, including the possibility of resonant reflection. We extend the analysis to chains of weakly coupled anharmonic oscillators and discuss the relevance of the effect for electronic transport spectroscopy of mesoscopic systems.

Phononic and photonic crystals for sensing applications

Abstract: Photonic and phononic crystals provide a novel and alternative platform for sensing material properties with high sensitivity. The sensor aims to determine properties of the fluid such as its nature, concentration or temperature, employing specific features in the photonic and phononic transmission spectra. The dependence of such frequency dips or peaks where the transmission takes place is correlated to material properties, specifically to the acoustic or optical refractive index through the light and sound velocity of the fluid. Looking at both phononic and photonic behaviors within one single platform increases the ability to determine the fluid properties by cross correlating the optical and acoustic data. The capability of the concept is demonstrated through two different structures for which different specific applications can be reached. The first one is made of a two-dimensional crystal constituted of infinite cylindrical holes in a silicon substrate where one row of holes oriented perpendicular to the propagation direction is filled with a liquid. In the second one, the transmissions of optical and acoustic waves are normally impinging upon a periodic perforated silicon plate where the embedded medium is a liquid. Finally, we introduce acoustic metamaterials made of hollow pillars deposited on a plate for sensing purposes. Such crystals can exhibit confined whispering gallery modes around the hollow parts of the pillars. Filling the hollow parts with a fluid gives rise to new localized modes, which depend on the physical properties and height of the fluid. In all the investigated cases, we show an ultra-sensitivity to the light and sound velocities for different fluids, considered as the analyte, depending on their nature, concentrations or temperature.