Sreemanta Mitra
@gitam.edu
Assistant Professor, Physics
GITAM University
EDUCATION
B.Sc., M.Sc., Ph.D.
RESEARCH INTERESTS
Experimental Condensed Matter Physics
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Aparna Parappurath, Sreemanta Mitra, Gagandeep Singh, Navkiranjot Kaur Gill, Tanweer Ahmed, T. Phanindra Sai, Kenji Watanabe, Takashi Taniguchi, and Arindam Ghosh
American Physical Society (APS)
Sreemanta Mitra, Saloni Kakkar, Tanweer Ahmed, and Arindam Ghosh
American Physical Society (APS)
Sreemanta Mitra, Divya Srivastava, Shib Shankar Singha, Saurav Dutta, Biswarup Satpati, Maarit Karppinen, Arindam Ghosh, and Achintya Singha
Springer Science and Business Media LLC
We discuss the effect of the in-plane electric field on the Raman spectroscopy for few-layered MoS2. The characteristic Raman modes of MoS2 show gradual red shift, while the intensity increases by 45–50% as the electric field is increased, showing a large electro-optical effect. Structural analysis suggests that our few-layered MoS2 belongs to P6/m2 space group with broken inversion symmetry. We attribute this gradual red shift to this broken symmetry-driven piezoelectricity in MoS2, which generates tensile strain along the perpendicular direction when the electric field is applied. The enhancement of the effect upon reversing the electric field direction adds credence to our interpretation. Our first principal density-functional theory calculation further substantiates the claim. This optical probing of the electromechanical coupling may lead to applications as a nonextensive technique for electric field/strain sensors in the nanoelectronics devices.
Sreyan Raha, Sreemanta Mitra, Prasanna Kumar Mondal, Subhajit Biswas, Justin D Holmes, and Achintya Singha
IOP Publishing
Electric field enhancement in semiconductor nanostructures offers a possibility to find an alternative to the metallic particles which is well known for tuning the light-matter interaction due to its strong polarizability and size-dependent surface plasmon resonance energy. Raman spectroscopy is a powerful technique to monitor the electric field as its scattering depends on the electromagnetic eigenmode of the particle. Here, we observe enhanced polarized Raman scattering from germanium nanowires of different diameters. The incident electromagnetic radiation creates a distribution of the internal electric field inside the naowires which can be enhanced by manipulating the nanowire diameter, the incident electric field and its polarization. Our estimation of the enhancement factor, including its dependence on nanowire diameter, agrees well with the Mie theory for an infinite cylinder. Furthermore, depending on diameter and wavelength of incident radiation, polarized Raman study shows dipolar (antenna effect) and quadrupolar resonances, which has never been observed in germanium nanowire. We attempt to understand this polarized Raman behavior using COMSOL Multiphysics simulation, which suggests that the pattern observed is due to photon confinement within the nanowires. Thus, the light scattering direction can be toggled by tuning the polarization of incident excitation and diameter of non plasmonic nanowire.
Tara Shankar Bhattacharya, Sreemanta Mitra, Shib Shankar Singha, Prasanna Kumar Mondal, and Achintya Singha
American Physical Society (APS)
Sreemanta Mitra, Jeremy Goh Swee Kang, John Shin, Jin Quan Ng, Sai Swaroop Sunku, Tai Kong, Paul C. Canfield, B. Sriram Shastry, Pinaki Sengupta, and Christos Panagopoulos
American Physical Society (APS)
The change of a material's electrical resistance (R) in response to an external magnetic field (B) provides subtle information for the characterization of its electronic properties and has found applications in sensor and storage related technologies. In good metals, Boltzmann's theory predicts a quadratic growth in magnetoresistance (MR) at low B and saturation at high fields. On the other hand, a number of nonmagnetic materials with weak electronic correlation and low carrier concentration for metallicity, such as inhomogeneous conductors, semimetals, narrow gap semiconductors and topological insulators, and two dimensional electron gas, show positive, nonsaturating linear magnetoresistance (LMR). However, observation of LMR in single crystals of a good metal is rare. Here we present low-temperature, angle-dependent magnetotransport in single crystals of the antiferromagnetic metal, ${\\mathrm{TmB}}_{4}$. We observe large, positive, and anisotropic MR(B), which can be tuned from quadratic to linear by changing the direction of the applied field. In view of the fact that isotropic, single crystalline metals with large Fermi surface (FS) are not expected to exhibit LMR, we attribute our observations to the anisotropic FS topology of ${\\mathrm{TmB}}_{4}$. Furthermore, the linear MR is found to be temperature independent, suggestive of quantum mechanical origin.
Jennifer Trinh, Sreemanta Mitra, Christos Panagopoulos, Tai Kong, Paul C. Canfield, and Arthur P. Ramirez
American Physical Society (APS)
The 1/8 fractional plateau phase (1/8 FPP) in Shastry-Sutherland lattice (SSL) spin systems has been viewed an exemplar of emergence on an Archimedean lattice. Here we explore this phase in the Ising magnet TmB_{4} using high-resolution specific heat (C) and magnetization (M) in the field-temperature plane. We show that the 1/8 FPP is smoothly connected to the antiferromagnetic phase on ramping the field from H=0. Thus, the 1/8 FPP is not a distinct thermodynamic ground state of TmB_{4}. The implication of these results for Heisenberg spins on the SSL is discussed.
Sreemanta Mitra, Girish C Tewari, Diana Mahalu, and Dan Shahar
Springer Science and Business Media LLC
We study magneto-transport properties of several amorphous Indium oxide nanowires of different widths. The wires show superconducting transition at zero magnetic field, but, there exist a finite resistance at the lowest temperature. The R(T) broadening was explained by available phase slip models. At low field, and far below the superconducting critical temperature, the wires with diameter equal to or less than 100 nm, show negative magnetoresistance (nMR). The magnitude of nMR and the crossover field are found to be dependent on both temperature and the cross-sectional area. We find that this intriguing behavior originates from the interplay between two field dependent contributions.
S Mitra, S Banerjee, A Datta, and D Chakravorty
Springer Science and Business Media LLC
AbstractThe exotic physical properties of graphene have led to intense research activities on the synthesis and characterization of graphene composites during the last decade. The methods developed for preparation of such materials and the different application areas are reviewed. Mainly the inorganic nanostructure/graphene composites have been discussed. The techniques of ex-situ and in-situ hybridization respectively, have been pointed out.
Some of the application areas such as batteries, ultracapacitors for energy storage, fuel cells and solar cells for energy generation are discussed. The possible future directions of research are highlighted.
Sreemanta Mitra, Girish C. Tewari, Diana Mahalu, and Dan Shahar
American Physical Society (APS)
We study the low-temperature magnetotransport properties of several highly disordered amorphous indium oxide (a:InO) samples. Simultaneously fabricated devices comprising a two-dimensional (2D) film and $10\\text{\\ensuremath{-}}\\ensuremath{\\mu}\\mathrm{m}$-long wires of different widths were measured to investigate the effect of size as we approach the 1D limit, which is around 4 times the correlation length, and happens to be around 100 nm for a:InO. The film and the wires showed magnetic field ($B$)-induced superconductor to insulator transition (SIT). In the superconducting side, the resistance increased with decrease in wire width, whereas an opposite trend is observed in the insulating side. We find that this effect can be explained in light of charge-vortex duality picture of the SIT. Resistance of the 2D film follows an activated behavior over the temperature ($T$), whereas, the wires show a crossover from the high-$T$-activated to a $T$-independent behavior. At high-temperature regime the wires' resistance follow the film's until they deviate and became independent of $T$. We find that the temperature at which this deviation occurs evolves with the magnetic field and the width of the wire, which show the effect of finite size on the transport.
A. Doron, I. Tamir, S. Mitra, G. Zeltzer, M. Ovadia, and D. Shahar
American Physical Society (APS)
In certain disordered superconductors, upon increasing the magnetic field, superconductivity terminates with a direct transition into an insulating phase. This phase is comprised of localized Cooper pairs and is termed a Cooper-pair insulator. The current-voltage characteristics measured in this insulating phase are highly nonlinear and, at low temperatures, exhibit abrupt current jumps. Increasing the temperature diminishes the jumps until the current-voltage characteristics become continuous. We show that a direct correspondence exists between our system and systems that undergo an equilibrium, second-order, phase transition. We illustrate this correspondence by comparing our results to the van der Waals equation of state for the liquid-gas mixture. We use the similarities to identify a critical point where an out of equilibrium second-order-like phase transition occurs in our system. Approaching the critical point, we find a power-law behavior with critical exponents that characterizes the transition.
M. Ovadia, D. Kalok, I. Tamir, S. Mitra, B. Sacépé, and D. Shahar
Springer Science and Business Media LLC
In superconductors the zero-resistance current-flow is protected from dissipation at finite temperatures (T) by virtue of the short-circuit condition maintained by the electrons that remain in the condensed state. The recently suggested finite-T insulator and the "superinsulating" phase are different because any residual mechanism of conduction will eventually become dominant as the finite-T insulator sets-in. If the residual conduction is small it may be possible to observe the transition to these intriguing states. We show that the conductivity of the high magnetic-field insulator terminating superconductivity in amorphous indium-oxide exhibits an abrupt drop, and seem to approach a zero conductance at T < 0.04 K. We discuss our results in the light of theories that lead to a finite-T insulator.
O. Mondal, S. Mitra, M. Pal, A. Datta, S. Dhara, and D. Chakravorty
Elsevier BV
Abstract Graphene oxide is transformed to reduced graphene oxide by high energy ball milling in inert atmosphere. The process of ball milling introduces defects and removes oxygen functional groups, thereby creating the possibility of fine tuning the band gap of all intermediate stages of the structural evolution. A limit of the backbone sp 2 network structure has been found which should be able to accommodate defects, before amorphization sets in. The amorphization of graphene oxide is achieved rather quickly in comparison to that of graphite. From thermogravimetric and differential scanning calorimetric analysis along with Fourier transform infrared (FTIR) and Raman spectroscopic studies, it is found that the number of oxygen-containing groups decreases at a faster rate than that of aromatic double bonds with increasing ball milling time with a maximum limit of 3 h. Several characterization techniques (FTIR, Raman, UV–Visible and X-ray photoelectron spectroscopy) have confirmed that the material synthesized is, indeed, reduced graphene oxide.
A. Bose, A. Mandal, S. Mitra, S. K. De, S. Banerjee, and D. Chakravorty
Springer Science and Business Media LLC
Na-4 mica template has been used to grow NiS nanosheets within the nanochannels with thickness ~0.6 nm. DC and ac electrical properties of the nanocomposite in a pellet-form have been measured over temperature range 313–473 K at frequencies from 102 to 106 Hz. The dc resistivity variation as a function of temperature has been explained as arising due to a parallel combination of NiS nanosheets and Na-4 mica grains. The activation energies of conduction have been found to be 0.23 and 0.45 eV in temperature ranges 323–363 K and 363–424 K, respectively. The frequency exponent s obtained from ac data has a value 0.7 which signifies a three-dimensional movement of the charge carriers involved. The dielectric modulus has been analyzed by two phase laminar conductor model proposed by Isard. The activation energies of dc resistivity and relaxation time are in reasonable agreement with each other in the different temperature ranges measured.
Sreemanta Mitra, Achintya Singha, and Dipankar Chakravorty
IOP Publishing
Graphene/glass nanocomposite was synthesized by gelation of the glass in a solution with dispersed graphene sheets. Electrical transport measurements were carried out on pellets formed by cold pressing of composite powders. Resistivity showed a nonlinear increase as a function of temperature in the range 300–400 K. This has been explained as arising due to the phonon spectra of the glass affecting the movement of electrons in graphene. Raman studies confirmed the presence of phonons in the silicate glass phase. The dielectric relaxation spectra of the composites at different temperatures are consistent with the above mechanism of the electron–glass phonon interaction.
Dhriti Ranjan Saha, Amrita Mandal, Sreemanta Mitra, Mykanth Reddy Mada, Philip Boughton, Sri Bandyopadhyay, and Dipankar Chakravorty
AIP
Nanodimensional metallic silver was grown by electrodeposion technique in a semi solid polymer matrix of polyacrylamide. The whole structure looks like dendronic. The average particle diameter of the as grown metallic silver is 13 nm. Nanoindentation study of these nanoparticles shows modulus and hardness value as 103.93 GPa and 3.12 GPa respectively.
Sreemanta Mitra, Dhriti Ranjan Saha, Sourish Banerjee, and Dipankar Chakravorty
AIP
Graphene/Polyvinyl alcohol (PVA) nanocomposite was synthesized with a graphene content of 1wt%. Viscoelastic properties were studied using a Dynamical Mechanical Analyzer. The composite showed a higher storage modulus as compared to PVA up to 275K. Thereafter there was a crossover to a lower value. The glass transition temperature for the composite was found to be smaller by 26K than that of pure PVA. This is believed to be occurring because of a reduction of surrounding entanglements of the polymer molecules due to the presence of graphene sheets.
Sreemanta Mitra, Sourish Banerjee, and Dipankar Chakravorty
AIP Publishing
Graphene/(Poly)vinyl alcohol (PVA) composite film with thickness 60 μm was synthesized by solidification of a PVA solution comprising of dispersed graphene nanosheets. The close proximity of the graphene sheets enables the fluctuation induced tunneling of electrons to occur from one sheet to another. The dielectric data show that the present system can be simulated to a parallel resistance-capacitor network. The high frequency exponent of the frequency variation of the ac conductivity indicates that the charge carriers move in a two-dimensional space. The sample preparation technique will be helpful for synthesizing flexible conductors.
Sreemanta Mitra, Oindrila Mondal, Sourish Banerjee, and Dipankar Chakravorty
AIP Publishing
Nickel-adsorbed graphene was prepared by first synthesizing graphite oxide (GO) by modified Hummers' method and then reducing a solution containing both GO and Ni2+. Energy dispersive X-ray spectroscopy analysis showed 31 at. % nickel was present. Magnetization measurements under both dc and ac magnetic fields were carried out in the temperature range 2 K to 300 K. The zero field cooled and field cooled magnetization data showed a pronounced irreversibility at a temperature around 20 K. The analysis of the ac susceptibility data was carried out by both Vogel-Fulcher as well as power law. From dynamic scaling analysis, the microscopic flipping time τ0∼10−13s and critical exponent zν=5.9±0.1 were found, indicating the presence of conventional spin glass in the system. The spin glass transition temperature was estimated as 19.5 K. Decay of thermoremanent magnetization was explained by stretched exponential function with a value of the exponent as 0.6. From the results, it is concluded that nickel adsorbed gr...
Amrita Mandal, Sreemanta Mitra, Anindya Datta, Sourish Banerjee, Sandip Dhara, and Dipankar Chakravorty
AIP Publishing
Two dimensional wurtzite ZnS nanosheets with thickness of 0.6 nm are grown within the interlayer spaces of sodium fluorophlogopite mica (Na-4 mica) using ion-exchange-cum-solution treatment method followed by sulfidation treatment at 873 K. The presence of wurtzite ZnS is confirmed by x-ray diffraction, electron microscopy, and Raman scattering studies. The two dimensional form of ZnS gives rise to a strong quantum confinement with the band gap blue shifted by 1.7 eV. Thickness of the nanosheet is confirmed using atomic force microscopy. Raman scattering studies show higher order transverse optical modes due to increased deformation potential in reduced dimension. In contrast to red shift of optical phonon modes in phonon confinement model, a blue shift observed is ascribed to a compressive stress on ZnS nanosheets grown within Na-4 mica interlayer spaces. An additional band at 315 cm−1 is assigned to surface optical phonon. Unusual broadening in room temperature photoluminescence spectrum may be due to s...
Amrita Mandal, Anindita Bose, Sreemanta Mitra, Anindya Datta, Sourish Banerjee, and Dipankar Chakravorty
Elsevier BV
Nanoplates of NiS with thickness 0.6 nm were grown within the crystal channels of Na-4 mica. The thickness of the nanoplates is confirmed by atomic force microscopy. The nanocomposites exhibited multiferroic (both ferromagnetic and ferroelectric) behavior at room temperature. Ferromagnetism was adduced to an increase of surface defects as a result of the two-dimensional configuration of the sample. Ferroelectric behavior was explained as arising due to a small distortion in the crystal structure of NiS grown within the Na-4 mica channels. This was substantiated by the refined values of lattice constants as determined by profile matching of X-ray data by a computer program. A magnetodielectric effect was also observed in this nanocomposite with a change of 0.77% in the dielectric constant for a magnetic field of 0.6 T.
Sreemanta Mitra, Amrita Mandal, Anindya Datta, Sourish Banerjee, and Dipankar Chakravorty
Elsevier BV
Nanosheets of nickel with thickness equal to 0.6 nm have been grown within the interlayer spaces of Na-4 mica. The sheets are made up of percolative clusters of nanodisks. Magnetization characteristics indicate a superparamagnetic behavior with a blocking temperature of 428 K. The magnetic anisotropy constant as extracted from the coercivity data has been found to be higher than that of bulk nickel by two orders of magnitude. This is ascribed to a large aspect ratio of the nickel nanophase. The Bloch exponent is also found to be considerably different from that of bulk nickel because of a size effect. The Bloch equation is still found to be valid for the two dimensional structures.
Amrita Mandal, Sreemanta Mitra, Anindya Datta, Sourish Banerjee, and Dipankar Chakravorty
AIP Publishing
CdS nanosheets of thickness 0.6 nm were grown within the interlayer spaces of Na-4 mica. Magnetization measurements carried out in the temperature range 2–300 K showed the composites to have weak ferromagnetic-like properties even at room temperature. The saturation magnetization (MS) at room temperature was found to be higher than that reported for CdS nanoparticles. The higher value of MS may be ascribed to the presence of a large number defects in the present CdS system, due to a large surface to volume ratio in the nanosheets as compared to that of CdS nanoparticles. The nanocomposites exhibited a magnetodielectric effect with a dielectric constant change of 5.3% for a magnetic field of 0.5 T. This occurred due to a combination of magnetoresistance and Maxwell-Wagner effect as delineated in the model developed by Catalan.
Sreemanta Mitra, Amrita Mandal, Anindya Datta, Sourish Banerjee, and Dipankar Chakravorty
American Chemical Society (ACS)
Ferromagnetic behavior has been observed experimentally for the first time in nanostructured manganese. Ultrathin (∼0.6-nm) manganese nanosheets were synthesized inside the two-dimensional channels...
Sreemanta Mitra, Oindrila Mondal, Dhriti Ranjan Saha, Anindya Datta, Sourish Banerjee, and Dipankar Chakravorty
American Chemical Society (ACS)
Graphene-polyvinyl alcohol (PVA) nanocomposite films with thickness of 120 μm were synthesized by solidification of PVA in a solution with dispersed graphene nanosheets. Electrical conductivity data were explained as arising due to hopping of carriers between localized states formed at the graphene-PVA interface. Dielectric permittivity data as a function of frequency indicated the occurrence of Debye-type relaxation mechanism. The nanocomposites showed a magnetodielectric effect with the dielectric constant changing by 1.8% as the magnetic field was increased to 1 T. The effect was explained as arising because of Maxwell–Wagner polarization as applied to an inhomogeneous 2D, two-component composite model. This type of nanocomposite may be suitable for applications involving nanogenerators.