Author
Debnarayan Jana
Other affiliations: National Taiwan University
Bio: Debnarayan Jana is an academic researcher from University of Calcutta. The author has contributed to research in topics: Graphene & Density functional theory. The author has an hindex of 23, co-authored 127 publications receiving 2328 citations. Previous affiliations of Debnarayan Jana include National Taiwan University.
Papers published on a yearly basis
Papers
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7 citations
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17 Jul 2015
TL;DR: In this article, the optical anisotropy and magnetic properties of these trilayer heterostructures can be understood from the crystallographic stacking order and inherent crystal lattice symmetry, which suggest that the h-BN/SLG/h-BN could provide a viable route to graphene-based optoelectronic and spintronic devices.
Abstract: The dependence of the stability of single-layer graphene (SLG) sandwiched between hexagonal boron nitride bilayers (h-BN) has been described and investigated for different types of stacking in order to provide the fingerprint of the stacking order which affects the optical properties of such trilayer systems. Considering the four stacking models AAA-, AAB-, ABA-, and ABC-type stacking, the static dielectric functions (in case of parallel polarizations) for AAB-type stacking possesses maximum values, and minimum values are noticed for AAA. However, AAA-type stacking structures contribute the maximum magnetic moment while vanishing magnetic moments are observed for ABA and ABC stacking. The observed optical anisotropy and magnetic properties of these trilayer heterostructures (h-BN/SLG/h-BN) can be understood from the crystallographic stacking order and inherent crystal lattice symmetry. These optical and magnetic results suggest that the h-BN/SLG/h-BN could provide a viable route to graphene-based opto-electronic and spintronic devices.
7 citations
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23 Aug 20197 citations
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TL;DR: In this article, the authors introduced defects like bond rotation and the sifting of atoms along the non-bonding direction in graphene to come up with a new dynamically stable crystal with a 5-4, 4-5, 5-6-5 ring geometry.
7 citations
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TL;DR: In this paper, structural, spectroscopic and radiative emission characteristics of Eu-doped BaTiO3 (BT) nanosystem as compared to the pure BT system were reported.
Abstract: We report on the structural, spectroscopic and radiative emission characteristics of Eu-doped BaTiO3 (BT) nanosystem as compared to the pure BT system. The structural analysis was performed by X-ray diffraction (XRD) studies where the nanoscale BT sample exhibits a perovskite structure with most intense peak along (1 1 0) plane that depicts the preferred crystallographic orientation. Also, the diffraction peak intensity was found to be suppressed for Eu-doped BT nanosystem. The nature of radiative emission was evaluated via steady-state photoluminescence spectroscopy (PL) and positron annihilation spectroscopy (PAS). The improved radiative emission response, with Eu2+ doping, was believed to be accompanied by 4f65d→4f7 transitions in case of Eu-doped BT system. Whereas, PAS lifetime study of doped sample has revealed longer lifetimes indicating thereby partial substitution of Ti4+ by Eu2+ in BaTiO3 system.
7 citations
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28,685 citations
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14 Jul 1996TL;DR: The striking signature of Bose condensation was the sudden appearance of a bimodal velocity distribution below the critical temperature of ~2µK.
Abstract: Bose-Einstein condensation (BEC) has been observed in a dilute gas of sodium atoms. A Bose-Einstein condensate consists of a macroscopic population of the ground state of the system, and is a coherent state of matter. In an ideal gas, this phase transition is purely quantum-statistical. The study of BEC in weakly interacting systems which can be controlled and observed with precision holds the promise of revealing new macroscopic quantum phenomena that can be understood from first principles.
3,530 citations
01 Sep 1955
TL;DR: In this paper, the authors restrict their attention to the ferrites and a few other closely related materials, which are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present.
Abstract: In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.
2,659 citations
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TL;DR: In this paper, the authors address the nature of these height fluctuations by means of straightforward atomistic Monte Carlo simulations based on a very accurate many-body interatomic potential for carbon and find that ripples spontaneously appear due to thermal fluctuations with a size distribution peaked around 70 \AA which is compatible with experimental findings (50-100 \AA) but not with the current understanding of flexible membranes.
Abstract: The stability of two-dimensional (2D) layers and membranes is subject of a long standing theoretical debate. According to the so called Mermin-Wagner theorem, long wavelength fluctuations destroy the long-range order for 2D crystals. Similarly, 2D membranes embedded in a 3D space have a tendency to be crumpled. These dangerous fluctuations can, however, be suppressed by anharmonic coupling between bending and stretching modes making that a two-dimensional membrane can exist but should present strong height fluctuations. The discovery of graphene, the first truly 2D crystal and the recent experimental observation of ripples in freely hanging graphene makes these issues especially important. Beside the academic interest, understanding the mechanisms of stability of graphene is crucial for understanding electronic transport in this material that is attracting so much interest for its unusual Dirac spectrum and electronic properties. Here we address the nature of these height fluctuations by means of straightforward atomistic Monte Carlo simulations based on a very accurate many-body interatomic potential for carbon. We find that ripples spontaneously appear due to thermal fluctuations with a size distribution peaked around 70 \AA which is compatible with experimental findings (50-100 \AA) but not with the current understanding of stability of flexible membranes. This unexpected result seems to be due to the multiplicity of chemical bonding in carbon.
1,367 citations