Department of Physics

&ldquo;IIT Jodhpur is committed to impart quality education to facilitate the creation of qualified, competent and responsible human resources to meet the emerging technological challenges of the world. It is working towards creating an equitable learning platform that is positive, accessible and effective in the face of the modern societal and scientific advancements.

Flexibility in curriculum, in all its academic programs, encompassing elements of teaching, research, creativity, innovation and entrepreneurship is the most unique feature of IIT Jodhpur. The Department of Science and Technology (DST), under the National Mission on Cyber Physical Systems, has identified IIT Jodhpur as a Technology &amp; Innovation Hub in the area of Augmented Reality and Virtual Reality. The institute has also been nominated as the coordinator for the Jodhpur City and Knowledge Cluster by the Office of Principal Scientific Adviser, Government of India.

The sprawling 852-acre IIT Jodhpur campus is a majestic tribute to the deep-rooted diverse cultural heritage of the region. The campus is an architectural masterpiece, which is slated to become an international exemplar of sustainability with net-zero energy, and advanced water and waste management strategies.&rdquo;

IIT Jodhpur

We report an open three-state perturbed system that depends on the topological parameters, where the underlying Hamiltonian is varying quasi-statically. The effective system hosts two second order exceptional points (EP2s). Here a third order exceptional point (EP3) is encountered with simultaneous encirclement of two EP2s by adiabatic variation of topological parameters. We study the robust successive state-exchange around the EP3. Maintaining adiabaticity, we estimate the evolution of total phase accumulated by each of the interacting states during encirclement; where interestingly, the state common to the pairs of coupled state picks up three times phase shift of 2π as a signature of EP3. Such an exclusively reported scheme once implemented in an anisotropic optical waveguide can be exploited in potential applications of mode conversion, switching and lasing by manipulating topological parameters. © 2019 IOP Publishing Ltd.

World University root node

Physica Scripta

Topological dynamics of an adiabatically varying Hamiltonian around third order exceptional points

The appearance of topological singularities, namely exceptional points (EPs) is an intriguing feature of parameter-dependent open quantum or wave systems. EPs are the special type of non-Hermitian degeneracies where two (or more) eigenstates of the underlying system coalesce. In this paper, we present a three level non-Hermitian Hamiltonian which hosts three interacting eigenstates. The matrix elements are optimized in such a way that the intermediate eigenstate interacts with both the other states and the underlying system hosts at least two different second order EPs. This coupling scheme has proven to be highly effective to encounter higher order EPs. The impact of quasi-static parameter variation along a cyclic contour around the embedded EPs on the dynamics of interacting eigenvalues has been investigated comprehensively in the context of cascaded state conversion. Such dynamics of the eigenvalues show a clear signature of the third order EP. Moreover, we examine the accumulation of phases around the identified EPs and study the hallmark of phase exchange during cascaded state conversions accompanied by the parametric encirclement of the third order EP. A device level implementation of the scheme is possible exploiting multimode anisotropic waveguides or coupled waveguide systems. © 2019 IOP Publishing Ltd.

Encounter of higher order exceptional singularities and towards cascaded state conversion

The electromagnetic interference shielding effectiveness (EMI SE) of amorphous and annealed melt-spun ribbons having typical composition of Co72.5Si12.5B15, (Fe0.65Co0.35)83Si1.3B11.7Nb3Cu1, Fe80Si8B12 and Fe83Si2B13Nb2 were studied in the 0.2–8.5 GHz microwave range. The amorphous nature of the as-quenched ribbons was confirmed by X-ray diffraction patterns and differential scanning calorimetry (DSC). The flexible electromagnetic wave absorber ribbons of CoSiB, FeSiB, and FeCoSiBNbCu based alloys exhibit ∼99.99% attenuation of electromagnetic waves in the entire 0.2–8.5 GHz (L, S and C-band) range. Both as-quenched and annealed amorphous ribbons of Co72.5Si12.5B15 and Fe80Si8B12 are electromagnetically active and total electromagnetic shielding effectiveness (SET) of ribbons found to be ∼36 dB, ∼34 dB throughout the test range. The EMI shielding properties deteriorates for FeCoSiBNbCu and FeSiBNb based nanocomposite ribbons achieved by in-situ crystallization annealing. The electromagnetic shielding of magnetic ribbons is effected mainly by absorption mechanism due to high electrical resistivity and magnetic permeability. The CoSiB and FeSiB melt-spun ribbons can be a potential magnetic filler for military and stealth applications in L, S and C-band range. © 2019 Elsevier B.V.

Physica B: Condensed Matter

Electromagnetic interference shielding effectiveness of amorphous and nanocomposite soft magnetic ribbons

We study exciton-exciton annihilation in atomically thin black phosphorus using micro-transient absorption spectroscopy. Our results show a transition from 1D-to 2D-like interactions as we increase the exciton densities. © 2019 The Author(s) 2019 OSA.

2019 Conference on Lasers and Electro-Optics, CLEO 2019 - Proceedings

1D and 2D Like Exciton-Exciton Interactions in Atomically Thin Black Phosphorus

Grafting of aryl radicals generated by electrochemical reduction of aryldiazonium salts has been extensively studied on various surfaces. However, there exists two unclear aspects; the first one is the generality of the blocking ability of simple functional groups toward multilayer growth, and the second one is the electronic impact of substituent groups of aryl radicals on grafting efficiency. To address these aspects, we have studied the electrochemical functionalization of graphite using aryldiazonium salts having electron-donating or electron-withdrawing groups at the 3,4,5-positions. Atomic force microscopy investigation of the functionalized surfaces revealed the formation of monolayers for all aryldiazonium salts, and thus, nitro, carboxy, ester, methyl, and methoxy groups at the 3,4,5-positions of the benzene ring suppress polyaryl growth. The degree of grafting estimated by scanning tunneling microscopy imaging and Raman spectroscopy of the functionalized surfaces depends on the electronic state of the aryl radicals, in which the radicals with electron-donating groups show a high degree of functionalization, whereas those with electron-withdrawing groups exhibit a low degree of functionalization. We discuss several possibilities that affect grafting density. Though there are several factors, we hypothesize that one factor to explain the observed reactivity trend is the electronic property of the aryl radicals, namely, the relative position of the singly occupied molecular orbital energy levels of the aryl radicals with respect to the graphite Fermi energy level. © Copyright © 2019 American Chemical Society.

Langmuir

Steric and electronic effects of electrochemically generated aryl radicals on grafting of the graphite surface

By using an oriented electric field in a scanning tunneling microscope, one can locally control the condensation of boronic acids at the liquid/solid interface. The phase transition between self-assembled molecular networks and covalent organic frameworks is controlled by changing the polarity of the applied bias. The electric-field-induced phase transformation is reversible under ambient conditions. © 2019 American Chemical Society.

Journal of the American Chemical Society

Electric-field-mediated reversible transformation between supramolecular networks and covalent organic frameworks

In this article, we discuss the recent progress on controlled structural modification of 2D materials by means of molecular functionalization, with a focus on scanning probe microscopy techniques for their characterization. For many practical applications of these novel materials, it is necessary to tune their electronic and optical properties, and molecule-based functionalization is a powerful approach to reach this. We discuss recent covalent and non-covalent approaches, for functionalization of graphene, transition metal dichalcogenides, black phosphorus, and hexagonal boron nitride. Nanostructuring approaches and their impact on 2D materials’ properties are highlighted. © 2019, © 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

Advances in Physics: X

Chemical modification of 2D materials using molecules and assemblies of molecules

A new series of six isostructural molecular solids of the composition [{Al(H2O)6}{Ln(pda)3}].10H2O where Ln = Sm, Eu, Gd, Tb, Dy and Yb have been synthesized and structurally characterised. All the solids are built of three major building blocks: the lanthanide dipicolinate anion, {Ln(pda)3}3−, the counter cation, {Al(H2O)6}3+ and a hexameric water cluster in chair form. The cations and the anions supramolecularly aggregate forming a 2D H-bonded sheet; the sheets are further stabilised through hexameric water clusters in chair form and water molecules. The crystals containing Sm, Eu, Tb and Dy showed characteristic emission of lanthanide ions. © 2018 Elsevier B.V.

Inorganica Chimica Acta

Isostructural series of [{Al(H2O)6}{Ln(pda)3}].10H2O: Synthesis, structure and photoluminescence

Nonclassical properties of photon added and subtracted displaced Fock states are studied using various witnesses of lower- and higher-order nonclassicality. Compact analytic expressions are obtained for the nonclassicality witnesses. Using those expressions, it is established that these states and the states that can be obtained as their limiting cases (except coherent states) are highly nonclassical as they show the existence of lower- and higher-order antibunching and sub-Poissonian photon statistics, in addition to the nonclassical features revealed through the Mandel Q M parameter, zeros of Q function, Klyshko's criterion, and Agarwal–Tara criterion. Further, some comparison between the nonclassicality of photon added and subtracted displaced Fock states have been performed using witnesses of nonclassicality. This has established that between the two types of non-Gaussianity inducing operations (i.e., photon addition and subtraction) used here, photon addition influences the nonclassical properties more strongly. Further, optical designs for the generation of photon added and subtracted displaced Fock states from squeezed vacuum state have also been proposed. © 2019 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim

Fulltext

Annalen der Physik

Lower- and Higher-Order Nonclassical Properties of Photon Added and Subtracted Displaced Fock States

We report here on the complex magnetic structure and magnetocapacitance in NiF 2 , a non-oxide multifunctional system. It undergoes an anti-ferromagnetic transition near 68.5 K, superimposed with canted Ni spin driven weak ferromagnetic ordering, followed by a metastable ferromagnetic phase at or below 10 K. Our density functional calculations account for the complex magnetic structure of NiF 2 deduced from the temperature and the field dependent measurements. Near room temperature, NiF 2 exhibits a relatively large dielectric response reaching &gt;10 3 with a low dielectric loss of &lt;0.5 at frequencies &gt;20 Hz. This is attributed to the intrinsic grain contribution in contrast to the grain boundary contribution in most of the known dielectric materials. The response time is 10 μs or more at 280 K. The activation energy for such temperature dependent relaxation is ~500 meV and is the main source for grain contribution. Further, a large negative magneto capacitance &gt;90% is noticed in 1 T magnetic field. We propose that our findings provide a new non-oxide multifunctional NiF 2 , useful for dielectric applications. © 2019, The Author(s).