Department of Physics

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We report an unusual buildup of the quantum coherence in a qubit subjected to non-Hermitian evolution generated by a parity-time (PT) symmetric Hamiltonian, which is reinterpreted as a Hermitian system in a higher dimensional space using Naimark dilation. The coherence is found to be maximum about the exceptional points (EPs), i.e. the points of coalescence of the eigenvalues as well as the eigenvectors. The nontrivial physics about EPs has been observed in various systems, particularly in photonic systems. As a consequence of enhancement in coherence, the various formulations of Leggett-Garg inequality tests show maximal violation about the EPs. © 2021 IOP Publishing Ltd.

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Journal of Physics A: Mathematical and Theoretical

PT symmetric evolution, coherence and violation of Leggett-Garg inequalities

The reliability of quantum channels for transmitting information is of profound importance from the perspective of quantum information. This naturally leads to the question as how well a quantum state is preserved when subjected to a quantum channel. We propose a measure of quantumness of channels based on non-commutativity of quantum states that is intuitive and easy to compute. We apply the proposed measure to some well-known noise channels, both Markovian and non-Markovian, and find that the results are in good agreement with those from a recently introduced l1-norm coherence based measure. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature.

Quantum Information Processing

Quantumness of channels

Adsorption characteristics of carbon nanotubes (CNTs) intercalated with nickel is a subject of growing experimental and theoretical interest. In this manuscript adsorption of hydrogen gas on the surface of nickel intercalated multiwall carbon nanotubes (MWNTs) has been studied. It is expected that metal catalysts like nickel can have possible pattern of atoms and molecules on the surface of MWNTs with varying parameters like diameters, concentration of nickel & MWNTs for sorption kinematics. Distribution and strong interaction of Ni with the MWNTs could support. Thus, adsorption capacity of the hydrogen via the spillover effect is expected. Ni doped MWNTs composites have been examined by using X-ray diffraction (XRD), Fourier Transform (FT-IR) infrared spectroscopy, Sorption kinetics (Sievert's spectrometer), and Scanning Electron Microscopy (SEM). © 2020 Elsevier Ltd.

Materials Today: Proceedings

Adsorption characteristics of MWNTs via intercalation of nickel

We report a simple, consistent, and economical wet-chemical method for synthesizing a series of Fe-Ni nanocomposites by varying Fe and Ni fractions. Further, graphite wrapped Fe-Ni alloy nanoparticles in core-shell geometries are prepared by calcination of nanocomposites at 900°C under N2 gas. XRD studies reveal body-centered and face-centered (bcc/fcc) cubic Fe-Ni alloy core particles and hexagonal graphitic shell formation. More interestingly, a structural transition from bcc to fcc phase is also investigated with varying Ni concentration. The microstructural studies demonstrate ~10 nm graphitic shells together with a nearly spherical ~40 nm diameter Fe-Ni metallic core. These magnetic alloys showed the variation in magnetization and coercive fields with alloy compositions. The Fe-Ni core-shell material with the maximum magnetization is used for fabricating rubber-based composites by varying filler loading in the range 60–80 wt%. The utility of Fe-Ni/C alloy and rubber composite is categorized in terms of electromagnetic impedance matching for the entire X-band (8.2–12.4 GHz) frequency range based on the filler concentration and absorber thickness for microwave absorption applications. These core-shell alloy systems may show potential for stealth of strategic targets because of their very low density (~1.1 g/cc) and lesser thickness than conventional absorbers. © 2021

Journal of Alloys and Compounds

Impedance engineered microwave absorption properties of Fe-Ni/C core-shell enabled rubber composites for X-band stealth applications

The Janus WSSe monolayer is a new 2D direct band gap material attracting attention due to its unique physical and chemical properties. The lattice thermal conductivity is calculated using the self-consistent approach as well as single-mode relaxation time approximation. We notice that acoustic modes contribute mainly to the lattice thermal conductivity. Thermoelectric properties are investigated using the Seebeck coefficient, electrical conductivity, thermal conductivity, power factor, and figure of merit for pristine WSSe monolayer. The effect of strain on thermoelectric properties is also investigated. Interestingly, the tensile strain resulted in a lowering of the lattice thermal conductivity from 25.37 to 9.90 W m−1K−1. The valley degeneracy with biaxial strain in the valence and conduction band edges enhances the power factor. Thus, strain ultimately, improves the figure of merit from 0.72 (0.73) to 1.06 (1.08) under biaxial strain for n(p) carriers at 5 × 1020 cm−3 and 7 × 1020 cm−3, respectively. The thermoelectric efficiency of biaxial stained monolayer based device improved about 29% at 1500 K. These studies provide an avenue to engineer the thermoelectric properties using strain mediated valley degeneracy as the external stimuli. © 2020 Elsevier B.V.

Enhancing thermoelectric properties of Janus WSSe monolayer by inducing strain mediated valley degeneracy

We investigated a single heterojunction solar cell with stannite phase Cu2HgSnS4 as a new potential absorber material using the hybrid density functional theory for materials parameter and macroscopic device simulation studies for the photovoltaic response. The lattice constants are optimized using PBEsol and GGA exchange-correlation approach with mBJ parameterization and considering spin-orbit coupling effect on heavy element Hg, while strong correlation of Cu and Hg 3d electrons are taken into account by Hubbard parameter U = 0.52 Ry. The computed bandgap is -1.33 eV. The effective mass of electrons and holes in the respective band edges (electron in conduction band and the hole in the valence band) is 0.25 m0 and 0.91 m0, respectively. Further, the computed materials optoelectronic parameters are used to optimize the device performance by introducing a variation in minority carrier lifetime, defect concentration in Cu2HgSnS4 absorber, Cu2HgSnS4/CdS interface, and the absorber thickness to achieve a realistic photovoltaic response. The optimal conversion efficiency is 11.6\% after taking more realistic parameters in the considered single-junction solar cell. However, the maximum photovoltaic response >17\% can be achieved by controlling absorber and interface defects together with optimal carrier concentration.

SOLAR ENERGY

Theoretical DFT studies of Cu2HgSnS4 absorber material and Al:ZnO/ZnO/ CdS/Cu2HgSnS4/Back contact heterojunction solar cell

A global fit to current b ? sl+l- data suggests several new physics solutions. Considering either only one operator or a pair of similar operators at a time and new physics only in the muon sector, it has been shown that the three scenarios (I) C9NP &lt; 0, (II) C9NP = -C10NP, (III) C9NP = -C90NP can account for all the data. In order to discriminate between these scenarios one needs to have a handle on additional observables in b ? sµ+µ- sector. In this work, we study the transverse polarization asymmetry of K* polarization in B ? K*µ+µ- decay, AT, to explore its sensitivity to discriminate between the three scenarios. We show that a measurement of this asymmetry with an accuracy of one percent can pick out which new physics scenario is the true solution, at better than 3s C.L. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0).

Proceedings of Science

Discriminating new physics in b ? sµ+µ- via transverse polarization asymmetry of K* meson

Each tubulin protein molecule on the cylindrical surface of a microtubule, a fundamental element of the cytoskeleton, acts as a unit cell of a crystal sensor. Electromagnetic sensing enables the 2D surface of microtubule to act as a crystal or a collective electromagnetic signal processing system. We propose a model in which each tubulin dimer acts as the period of a one-dimensional crystal with effective electrical impedance related to its molecular structure. Based on the mathematical crystal theory with one-dimensional translational symmetry, we simulated the electrical transport properties of the signal across the microtubule length and compared it to our single microtubule experimental results. The agreement between theory and experiment suggests that one of the most essential components of any Eukaryotic cell acts as a one-dimensional crystal. © 2021 by the authors.

Crystals

Microtubules as one-dimensional crystals: Is crystal-like structure the key to the information processing of living systems?

Fibrillation of peptides and proteins is implicated in various neurodegenerative diseases and is a global concern. Aging leads to the formation of abnormal isoaspartate (isoAsp) residues from isomerization of normal aspartates in proteins, triggering fibril formation that leads to neurodegenerative diseases. Protein L-isoaspartyl methyltransferase (PIMT) is a repair enzyme which recognizes and converts altered isoAsp residues back to normal aspartate. Here we report the effect of gold nanoparticles (AuNPs) of different sizes on the structure and function of PIMT. Spherical AuNPs, viz. AuNS5, AuNS50 and AuNS100 (the number indicating the diameter in nm) stabilize PIMT, with AuNS100 exhibiting the best efficacy, as evident from various biophysical experiments. Isothermal titration calorimetry (ITC) revealed endothermic, but entropy driven mode of binding of PIMT with all the three AuNSs. Methyltransferase activity assay showed enhanced activity of PIMT in presence of all AuNSs, the maximum being with AuNS100. The efficacy of PIMT in presence of AuNS100 was further demonstrated by the reduction of fibrillation of A beta 42, the peptide that is implicated in Alzheimer's disease. The enhancement of anti-fibrillation activity of PIMT with AuNS100 was confirmed from cell survival assay with PC12 derived neuronal cells against A beta 42 induced neurotoxicity.

SCIENTIFIC REPORTS

Effect of gold nanoparticles on the structure and neuroprotective function of protein L-isoaspartyl methyltransferase (PIMT)

The physics of exceptional point (EP) singularities has been a key to a wide range of unique physical applications in open systems. In this context, the mutual interactions among four coupled states around a fourth-order EP (EP4) in a physical system is yet to be explored. Here we investigate the unique features of an EP4 in a fabrication feasible planar optical waveguide with a multilayer gain-loss profile based on only two tunable parameters. Following a quasistatic gain-loss around the embedded EP4, a unique fourth-order successive switching phenomenon among the propagation constants (β values) of four coupled modes has been explored. An exclusive chiral light dynamic following the dynamical variation of the gain-loss profile has been reported for the first time, which enables a special type of asymmetric higher-order mode conversion scheme. Here all the coupled modes associated with an EP4 are fully converted into different specific higher-order modes based on the choice of encirclement directions. The proposed scheme would present EP4 as a new light manipulation tool for integrated photonic devices. © 2021 Optical Society of America