Research

Collapse All
Expand All

The research activity of condensed matter experiment (CME) group at the Physics department of IIT Delhi covers a wide range of topics such as (i) nanostructured materials, thin films and devices, (ii) novel magnetic multifunctional and topological materials, (iii) spintronics and magnetism, and (iv) optical properties of condensed matter e.g., ultrafast dynamics of condensed matter with femtosecond laser. CME group houses several specialized experimental laboratories as well as several departmental facilities. The CME group has close links with Nanoscale research facilities of the institute that houses a clean room as well as several characterization facilities. At present, the department has a X-Ray diffractometer, a X-ray photoelectron spectroscopy, a SQUID magnetometry, a physical property measurement system, ultrafast-optics laboratory (also housing a Raman spectrometer and a photoluminescence set-up), a pulse laser deposition system, and an atomic force microscope as departmental facilities. Individual research labs also have several state-of-art facilities, the details of which can be found by visiting the corresponding laboratory web pages.

Nanostructured Materials, Thin Films, and Devices

We also focus on following activities. 2D materials, 2D-3D interfaces and devices for thermoelectric, photovoltaic, LEDs, photo-electrochemical and gas sensor applications. Growth of metal, semiconductor, hybrid, alloy and core-shell nanoparticles and nanostructure/nano- composites for specialized applications such as water splitting for hydrogen production, nanogenerator for harnessing mechanical energy, thermoelectric devices, solar cells, microwave tunable filters, resistive switching memories. Physical properties of complex oxide heterostructures at nanoscale for energy storage applications and electron-correlated materials, study of condensed matter using scanning kelvin probe, SQUID, conducting atomic force and thermal microscopy, conventional absorption and PL spectroscopy, and advanced spectroscopies such as surface enhanced Raman spectroscopy (SERS), CARS etc.

Faculty associated: B. R. Mehta, Neeraj Khare, P. Srivastava, Santanu Ghosh, R. S. Dhaka, J.P. Singh, R. Singh, M. C. Bhatnagar, and G. Vijaya Prakash

Novel Magnetic Multifunctional Materials

We focus on “Smart magnetic multifunctional materials” such as (i) Magnetic Shape Memory Alloys, (ii) Multiferroic materials with magnetoelectric coupling, (iii) Topological insulators, (iv) Multifunctional Huesler alloys for spintronics, (v) non-linear antiferromagnets for spin-orbit torque.

Faculty associated: R. Chatterjee, S. Chaudhary, P. K. Muduli, Neeraj Khare, Santanu Ghosh, R. S. Dhaka

Spintronics and Magnetism

We focus on emerging areas such as the spin Hall effect and its inverse, spin-orbit torques, magnetic skyrmions, spintronic based THz emitters, and 2D-spintronics. Magnetoresistive Tunnel Junctions (MTJ) for ultrahigh sensitive magnetic field sensors, microwave oscillators and next generation Magnetic Random Access Memories (MRAMs), Transparent Ferromagnetic Semiconducting (FMS) oxides for semiconductor spintronics, growth and characterization of epitaxial half-metallic (100% spin polarized) ferromagnetic thin films, fabrication of spin ice structures, magnetism in bulk and thin Films of metallic ferromagnets, Heusler alloys, superconducting oxides and other oxides.

Faculty associated: R. Chatterjee, S. Chaudhary, P. K. Muduli, Santanu Ghosh, P. Das, S. Manna, R. S. Dhaka

Optics of Condensed Matter

Our research interest is in the interdisciplinary areas of condensed matter physics and photonics using continuous wave (CW) as well as ultrafast femtosecond(fs) lasers to study a variety of condensed matter systems. The THz research activities are broadly based on: (a) investigating the ultrafast carrier dynamics of different materials using ultrafast UV pump – THz probe studies, (b) studying the effect of extreme P-T conditions to provide a new route toward discovering advanced structural materials and new materials with enhanced performance for energy transformation, and (c) understanding the large-scale behavior of the Earth and other planets through experimental study of geological materials and minerals under extreme P-T conditions.

Faculty associated: S. Kumar, G. Vijaya Prakash, A. Sengupta

We work in interdisciplinary areas of condensed matter physics with broad research interest in first principles based simulation of designing new materials and understanding their properties using state-of-the-art density functional theory (DFT) and beyond methods. We predict properties of materials by integrating different level of theories and validate our prediction using the highest level of theoretical approaches within the DFT framework or by comparing with experimental data (if available). Most of the materials we design have significant impact in materials science. In addition, we aim at developing theoretical methods that allow us in understanding general rules of a given problem in materials science. We solve the problem by including electronic correlation effects by combining DFT with quantum chemistry methods (eg. HF, MP2, CCSD) and their applications to solve multiscale and multidisciplinary research problems. In order to capture the effect at finite temperature and pressure to mimic real experimental environment, we employ the ab initio atomistic thermodynamics and beyond approaches.

Faculty associated: Saswata Bhattacharya, Rohit Narula, Brajesh Mani, Sankalpa Ghosh

Computational Materials Modelling

We work in interdisciplinary areas of condensed matter physics with broad research interest in first principles based simulation of designing new materials and understanding their properties using state-of-the-art density functional theory (DFT) and beyond methods. We predict properties of materials by integrating different level of theories and validate our prediction using the highest level of theoretical approaches within the DFT framework or by comparing with experimental data (if available). Most of the materials we design have significant impact in materials science. In addition, we aim at developing theoretical methods that allow us in understanding general rules of a given problem in materials science. We solve the problem by including electronic correlation effects by combining DFT with quantum chemistry methods (eg. HF, MP2, CCSD) and their applications to solve multiscale and multidisciplinary research problems. In order to capture the effect at finite temperature and pressure to mimic real experimental environment, we employ the ab initio atomistic thermodynamics and beyond approaches.

Faculty associated: Saswata Bhattacharya, Rohit Narula, Brajesh Mani

Atomic and Many-atom Complex systems

We develop and use the computational tools to probe the fundamental physics and related technological applications for atomic and many-atomic complex systems. For single atom or ion, we develop Relativistic Coupled-Cluster based theories and sophisticated codes and probe various fundamental physics such as atomic clocks, parity and time-reversal violations, anopole moment, and the search for the variation in the fundamental constants. For condensed matter systems, we develop the first-principles based atomistic models to simulate the properties at finite temperatures. For properties at zero Kelvin we use Density Functional Theory and based methods. Some properties of our interest include electronic and band structure, dielectric, pyroelectric, piezoelectric, flexoelectric, caloric, magnetization and magnetic properties, phonons, magnons and electromagnons in complex (anti)ferroic oxides bulk and nanostructures.

Faculty associated: Brajesh Mani

Light-Matter Interaction in $sp2$ Carbons

Here we delve the interaction of light with nanoscale aggregations of graphitic ($sp^2$-hybridized) carbons such as single, multi-layer, dot-like and twisted graphenes, and pristine and functionalized carbon nanotubes (CNTs) using a combination of many-body theory and high-precision computational (ab initio, and numerical) modelling techniques for investigating their electronic and vibrational properties and optical response. Currently, we're interested in elucidating and finding experimental signatures for higher spectroscopies such as second-order Raman scattering in the framework of exciton-polariton scattering which results in lower-dimensional carbons due to the diminished screening between their charge carriers. We're also exploring the possibility of indirect-exciton formation in twisted bilayer graphene which is particularly exciting given the strong possibility of prominent electron corrections effects at magic angles. Using ab initio calculation we're also exploring the viability and rational design of real-world functionalized CNT metastable photoswitches and single-photon emitters (SPEs).

Faculty associated: Rohit Narula, Sankalpa Ghosh

We work in the area of Statistical and Computational Physics which is devoted to understanding macroscopic assemblies of identical particles. Since such systems abound in nature, the scope of the subject is vast. We have studied diverse systems, many within the realm of condensed matter physics, some at the interface of statistical physics and bio-medicine and some at the interface of statistical physics and optics. Our recent research problems are on complex spin systems (dipolar magnets, spin glasses and quantum glasses), complex fluids (liquid crystals with nano-inclusion) and emergent properties of magnetic nanoparticle assemblies. We use analytical techniques from equilibrium and non-equilibrium statistical physics along with computational techniques such as Monte Carlo, parallel tempering, molecular dynamics, graph cuts, etc. Many of these studies are strongly driven by experiments which have reinforced and complemented our theoretical formulations.

Faculty associated: Varsha Banerjee

Miniature heat engines generally referred to as micro-engines constitute a fascinating field of current research. These engines consist of a single or a few microscopic particles or spins (called as a working substance), and are driven by an external time dependent force. Hence, taking the system out of equilibrium. Due to the smallness of the system, fluctuations dominate over the mean values of the thermodynamic quantities like work, heat, entropy etc. For such inherently non-equilibrium systems, average values of the thermodynamic quantities are insufficient and full probability distributions need to be studied. Due to a very noisy environment micro-engines perform poorly in terms of efficiency, reliability when compared with thermodynamic engines like Carnot, Stirling Engines. My group at IIT, Delhi tries to understand such micro engines with newly developed technique of "Stochastic Thermodynamics". We are also extending these studies to active particle systems e.g. bacteria. We are also studying Quantum Particle and Heat Transport in mesoscopic systems.

Faculty associated: Rahul Marathe

Understanding the swimming of micro-organism in complex environment is very important for a variety of medical applications. We try to model both natural as well as artificial swimmer in Newtonian as well as non-Newtonian fluids. One area of focus is how micro-organism adopt different strategies to survive in harsh environment they live. Another area of particular interest is to model protein aggregation using patchy colloidal particles. Here we focus on the bundle formation of amyloid fiber responsible for many neuro degenerative diseases. The isotropic as well as anisotropic particles aggregation and dynamics are studied using the tools of equilibrium and non-equilibrium statistical mechanics.

Faculty associated: Sujin B Babu

Everyday we encounter hundreds of matters and forces (e.g., electrical, mechanical, gravitational, etc.) around us. The diversity of matters and forces raises two rational questions: (1). what are the matters composed of? and (2). are these forces all distinct or someway connected? High Energy Physics (HEP) aims to answer these questions: it probes the most elementary units of the matter and investigates fundamentals interactions among those basic constituents. The foundation of the HEP, which attempts to address the aforesaid queries, is known as the Standard Model (SM) of particle physics. The SM houses only elementary entities like leptons, quarks, photon, W & Z bosons, gluons and Higgs boson. Some of these (leptons, quarks) act as the foundation of all matters, some others are (photon, W & Z bosons, gluons) responsible for mediating fundamental (electromagnetic, weak and strong, respectively) interactions while the Higgs boson appears instrumental for mass generation. The success of SM in understanding mother nature is truly magnificent and has already bagged more than twenty Noble prizes.

The stupendous success of the SM is, however, not impeccable. There exists theoretical glitches (e.g., hierarchy problems, unification of all fundamental interactions including gravity, etc.) as well as experimental anomalies (e.g., non-zero neutrino masses and mixing, hints of dark matter from galaxy rotation curve, matter-antimatter asymmetry of the Universe, etc..) that demands physics beyond the SM to reveal the mysteries of our Universe.

The HEP group of IIT Delhi is actively involved in the following research domains:

Brief Research activity of Physics of strongly interacting matter (a group of seven PhD scholars and one post-doctoral researcher led by Prof. Amruta Mishra)

The medium modifications of the properties of hadrons at high temperatures and/or densities is relevant to the neutron star phenomenology, as well as, for the ongoing and the future relativistic heavy ion collision experiments, where the experimental observables are affected by the medium modifications of the hadrons. Through heavy ion collision experiments, the strongly interacting matter is created in the laboratory, and the varying experimental conditions like the collision energy, impact parameter and the colliding ions give a broad regime in the temperature and density of this excited nuclear matter. Experiments have been performed at Schwer-Ionen-Synchrotron (SIS) at Gesellschaft fuer Schwerionenforschung (GSI) in Darmstadt, Germany, Alternating Gradient Synchrotron (AGS) in Brookhaven National Laboratory (BNL) in U.S.A., at Super-proton-Synchrotron (SPS) at CERN, Geneva, at the Relativistic Heavy Ion Collider (RHIC) at BNL, at Large Hadron Collider (LHC) at CERN, and, planned at the Facility for Antiproton and Ion Research (FAIR) at GSI, Germany, which will be operational in the near future. In the ultra-relativistic heavy ion collisions, strong magnetic fields (∼ 6 times 1018 Gauss at RHIC and ∼ 1019 Gauss at LHC) are created and magnetic fields are also known to exist in neutron stars/magnetars. This has initiated intense work on the properties of hadrons in the presence of magnetic fields. Isospin asymmetric effects are also important in high energy nuclear collision where the colliding heavy ions are are neutron rich.

A chiral effective model is adopted to study the effects of density, temperature, isospin asymmetry as well as magnetic fields on the properties of the hadrons.A chiral SU(3) model constructed by using the symmetries of QCD at low energies,is generalized to include the hadrons with heavy flavour quarks/antiquarks. The heavy flavour mesons, e.g., open charm (bottom) mesons as well as charmonium and bottomonium states, have been studied within the chiral effective model. The masses of the heavy quarkonium states are calculated from a dilaton field, which mimicks the gluon condensates of QCD.The decay widths of the charmonium (bottomoium) states to D Dbar (B Bbar) in the magnetized hadronic matter are studied using a quark pair creation model, namely 3P0 model, as well as using a field theoretic model for composite hadrons with quark constituents. These studies should have observable effects on the production of the hidden and open heavy flavour mesons in heavy ion collision experiments. The density and isospin asymmetry effects on the masses of the D- and B-mesons are observed to be particularly important, which should be observed in their production, as well as, D/Dbar and B/Bbar ratios, in the asymmetric nuclear collisions at the Compressed Baryonic Matter (CBM) experiment of the proposed project FAIR at GSI, Germany.

Brief Research activity of Beyond the SM phenomenology (a team of two PhD scholars led by Dr. Pradipta Ghosh)

Physics beyond the SM (BSM) remains inescapable even after Higgs discovery in 2012 to answer a few doubts where the SM appears inept. On the other hand, apart from the detection of neutrino masses (bagged 2015 Noble prize), any confirmed discovery from BSM territory (e.g., the dark matter) remains missing till to date. The latter has indeed questioned the existence of BSM physics within experimental reach. In this despondent time we are promoting the idea of complementary searches together with modified search strategies that might act as the saviour. In brief, we identify a few BSM scenarios where the same set of parameters are instrumental in generating different BSM signals like, neutrino masses and mixing, dark matter, charged lepton flavour violation, same sign di-leptons and/or displaced vertices at colliders, etc, etc. Subsequently, we scrutinize the concerned parameter space by using limits/bounds from experiments that are sensitive to different sectors (e.g., neutrino and flavour violation or neutrino and dark matter). Finally, with the help of experimental colleagues, we also propose modified search methods that could help us to detect the much anticipated BSM physics.



Brief Research activity of Strong force phenomenology (a team of two PhD scholars led by Dr. Tobias Toll )

Our research interests lie primarily in the strong interactions which are an integral part of The Standard Model. We are particularly interested in the processes which are sensitive to high gluon densities like Exclusive Vector Meson production and as it turns out we can extract information about the proton’s profile and fluctuations from coherent and incoherent cross-sections of these processes. We test the feasibility of such measurement by the means of simulated data using the event generator Sartre. Our work includes implementing these fluctuations in Sartre and improving upon the present models. We plan to include the higher order corrections as future work-plan.

Ion-atom collision physics

My area of interest is collision of highly charged ions interaction with atoms, molecule of biological interest, clusters and ices of bio-and astrophysical relevance. My work involves low and high energy accelerators (keV/u – MeV/u energies). The collisions products, ions/electrons/ radicals are analysed with several techniques including Time-of-flight, electron spectrometers and Cold Target Recoil Ion Momentum Spectrometers (COLTRIMS). These studies are of great interest for the bio-medical application to estimate the damages to the human DNA/ RNA caused by exposure to ionizing radiation. Also, the experiments can simulate the astronomical phenomena such as evolution of larger molecules by irradiation of small molecules by cosmic rays.

Faculty associated: Aditya Narain Agnihotri

Cold atom quantum technology

The beauty of cold atom based quantum technologies is that, one can design versatile quantum systems and fully control their properties by simple and clever approaches, just because of the inherent quantum nature of atoms and photons. In one approach we cool atoms to million times colder than room temperature using precisely frequency tuned lasers. In a second approach we trap these cold atoms in optical potentials even to the single particle level. With these abilities, we can design textbook like quantum systems with few individually addressable atoms. The real world problems demand to build large quantum systems beyond textbook examples. The biggest challenge in achieving this goal is to know how to control the environment induced decoherence. In our research group we aim to address these open problems in a step by step manner. These technological and conceptual developments will lead us to build large scale quantum information processing network, quantum computation protocols for solving industry and society relevant problems, quantum sensing devices and quantum metrology modules for precision instrumentations and measurements.

Faculty associated: Bodhaditya Santra

Magnetics & Advanced Ceramics Lab

Our group works on topological classification of semi-metals using experimental and DFT simulations. Topological semi-metals are classified as a quantum phase of matter that host Dirac and Weyl fermions. The researchers working in the area of quantum matter physics, study the transport properties of these exotic materials under very low temperature, high magnetic field and high pressures. Our group has worked on Bi Selenide / Telluride single crystal Topological Insulator (TI) and have demonstrated 3D TI behavior in these crystals. Presently we are working on rare earth based Half Heusler (HH) alloy systems for their non-trivial surface states. The general formula of these XYZ HH alloy systems, where X can be any rare earth element like Dy, Er, Yttrium etc., Y is generally transition element Pd, Pt, Au and Z is usually heavy element proving SOC like. Bi, Sb, etc.; show interesting surface state properties.

Faculty associated: Ratnamala Chatterjee

Plasmas are known to be the fourth state of matter which is formed when one or more electrons of a large fraction of the constituent atoms of a gas are removed by supplying them energy larger than their ionization energy. However, not all the atoms are in ionized state and therefore a plasma basically comprises of three kinds of species, namely electrons, ions and neutrals. They are known to constitute more than 99% of the visible matter in our universe and therefore attract a wide research interest.

In the plasma physics division of our department, we are primarily working in the broad research areas of high intensity laser-plasma interactions, plasma-material interaction and dusty plasmas. Areas of particular research interest are laser-plasma based charged particle acceleration, fast ignition, relativistic electron beam propagation, magnetic field generation, x-ray laser excited nanoplasmas, terahertz (THz) radiation generation, nonlinear waves including solitons, Hall thrusters, particle acceleration and density modulation by microwaves, plasma / surface nitriding, visco-elastic effects in dusty plasmas, and turbulence in laboratory and astrophysical plasmas. We employ theoretical as well as numerical methods, namely, hydrodynamics, molecular dynamics and particle-in-cell (PIC) techniques to investigate some of the key questions in the above areas and also perform experiments in some of the areas.

Laser-plasma based charged particle acceleration

Plasmas can support very high electric fields, several orders of magnitude larger than those supported by the modern RF accelerators, owing to the fact that they are already broken down unlike materials which can sustain electric fields below a value for which field ionization becomes prominent. This makes plasmas ideal candidates for charged particle acceleration in relatively shorter distances (~ few meters as a whole system) as compared to several kilometers large RF accelerators currently under operation, e.g., LHC@CERN. Both electrons as well as ions can be accelerated using schemes involving high intensity lasers interacting with plasmas. Techniques to improve the beam quality (monoenergeticity and reduced spread) and to increase the beam current are some areas of active research interest. We employ theoretical models as well as some massively parallel PIC codes for investigating current issues related to the laser-plasma based ion acceleration schemes, namely, target normal sheath acceleration and radiation pressure acceleration.

Faculty associated: H.K. Malik, A. Das, V. Saxena

Modeling of laboratory plasmas

We are also interested in modeling laboratory experiments pertaining to electron cyclotron resonance based large volume uniform plasma production with potential applications in generating negative hydrogen ion beams for fusion applications as well as in efficient electrodeless plasma thruster applications. For these studies, we closely collaborate with the Plasma Physics Lab (PPL) of Centre for Energy Studies (CES), IIT Delhi, where these experiments are being carried out.

Faculty associated: A. Das, V. Saxena

Visco-elastic effects in dusty plasmas

A dusty plasma comprises of electrons, ions, neutrals and micron sized dust particles with very high negative charge. As for such plasmas, the electrostatic interaction is very strong, they are also termed as strongly coupled plasmas. Owing to this strong coupling effect these plasmas exhibit some solid like properties (e.g., elasticity) along with some fluid like characteristics (e.g., viscosity). These visco-elastic properties can be tuned by varying the strength of coupling which is mainly controlled by the background plasma parameters. In this context, different coupling regimes are investigated using generalized hydrodynamics as well as classical molecular-dynamics simulations.

Faculty associated: A. Das

X-ray laser excited nanoplasmas

Modern day x-ray sources boast of sub-angstrom wavelengths and ultra-short pulses with decent brightness. These x-ray sources are ideal candidates for imaging complex bio-molecules. However, to understand the physics involved, rare gas clusters are the perfect test beds as they can be easily prepared in varied sizes. Therefore, it is important to first understand the two phases of the nonlinear interactions of intense x-ray free electron laser pulses with these clusters: the first phase involving x-ray irradiation of the rare gas clusters dominated by photo processes, and the second phase of nanoplasma expansion dominated by collisional hydrodynamics. We model this whole process by a computationally efficient two stage semi-classical molecular dynamics – hydrodynamics scheme.

Faculty associated: V. Saxena

Terahertz (THz) radiation generation

We have suggested different methods for the efficient THz radiation generation through the interaction of laser with plasma, gas jet and nanostructures. A concept of efficient tunnel ionization has been established by employing the superposed field of two lasers in addition to the analytical calculations for the frequency of emitted radiation. Means have been discussed for the stronger and collimated radiation. On the other side, the role of laser pulse shape has been uncovered in getting stronger ponderomotive force for the generation of stronger current in the laser beating process. The use of external magnetic field for tuning the frequency, power, focus and polarization of the emitted radiation has been discussed in greater detail. Other concerns have been to achieve multifocal THz radiation for its medical applications and now our focus is to generate the THz radiation suitable for its spectroscopic applications.

Faculty associated: H.K. Malik

Instabilities and electron transport in Hall thrusters:

Hall thrusters are the space propulsion devices where Xe plasma is created and ions are accelerated to provide thrust to the device. However, owing to the gradient in density and magnetic field, and resistive coupling of oscillations with the electrons drift lead to various kinds of instabilities. We have focused on Rayleigh-Taylor (RT) instabilities and resistive instabilities. For the first time we showed analytically that there is a frequency band for the occurrence of RT instability. Also means to suppress these instabilities were discussed. Work is underway to find an appropriate profile of magnetic field for the suppression of such instabilities, in addition to both the electrostatic and electromagnetic resistive instabilities. The role of finite temperature of the ions is being talked about in this direction. The recent problems of dust generation due to the collisions of ions with the walls and the shut down of these devices are being addressed. The field of the instabilities is thought to be used for the electron transport and efficient plasma generation for increasing the efficiency of these devices. Also we are working toward designing of an efficient Hall thruster.

Faculty associated: H.K. Malik

Plasma-material interaction

Nitriding is an advanced future technology concerning the realization of improvement in mechanical and electrical properties simultaneously. In order to attain the suitability of the materials, low carbon steels and titanium fit very well for proper industrial and electronic device applications. However, there are several issues that need to be discussed before implementation of the materials. We aimed to improve the mechanical hardness by employing different approaches, viz. hot cathode arc discharge plasma and low energy ion beam implantation, and controlling the growth parameters. For this a hot cathode arc discharge plasma system has been developed for plasma nitriding where both the plasma and nitriding parameters could be controlled separately. We focused on low carbon steel and titanium for the hardness since the titanium is also recognized for its strategic importance as a unique light weight, high strength alloy, structurally efficient metal for critical, high-performance aircraft, such as jet engine and airframe components. Based on our experimental study with plasma nitriding and ion implantation for hardening of steel and titanium samples, it is easy to optimize the plasma parameters for achieving desired mechanical properties in these samples for their specific applications. In the above phenomenon, sheath plays a vital role which is responsible for modifications of surface and tribological properties of materials under investigation. The sheath formed in electronegative plasmas is designated as an electronegative sheath which has an immense application in various fields like thin films depositions, plasma chemistry, plasma-surface interactions, semiconductor industries, microelectronics industries, spacecraft propulsion and many more. The interaction of electronegative discharges with an absorbing surrounding plasma wall is an important problem for many applications, such as material processing, Langmuir probe diagnostics, and plasma sheath lenses. Hence, our focus is now on developing theoretical models to make an in depth study of the sheath formation and behaviour of plasma parameters in electronegative plasmas under the effect of an oblique and constant magnetic field, presence of collisions and charged species’ distinctive temperature, etc. Also experimental study on ion sheath formation and its modification due to different plasma parameters like dose, implantation time, the multiplicity of ions, etc. are underway for achieving desired properties of materials. During the nitriding process, change in temperature leads to the formation of different microstructure at the surface of the investigated material. So modifications of microhardness, corrosion resistance, etc. are also our objectives. In this direction, we are looking for a mechanism that enables us to control the electronegativity and temperature of negative ions through the energy exchange of microwave with the plasma electrons and their collisions with the negative ions. In collaboration with SSPL we are also working on plasma based passivation study for AlGaN/GaN using plasma enhanced chemical vapor deposition (PECVD) and inductively coupled plasma chemical vapor deposition (ICPCVD) techniques. Theoretical modelling is now being done for such systems used for plasma etching where dust contamination is the important ingredient.

Faculty associated: H.K. Malik

High energy particle beam interaction with materials

The physical properties of the materials are not only sensitive to the beam species, energy and their fluences, but also to the other beam parameters such as beam profiles, effective beam cross sections and emittances, during ion beam irradiation or implantations on the materials. We have uncovered the role of beam profiles and effective cross section of ion beam during ion-matter interactions in tailoring the physical properties of nanostructure materials during implantations of two kinds of beam species, C and N ion beams, in the ZnO thin films prepared by RF sputtering. It was revealed that the ferromagnetism, bandgap energy, grain size, crystallinity, electrical and many other structural, morphological, compositional and optical properties can be engineered and tuned by varying the ion beam profiles and effective beam cross sections of the incident ion beam and keeping other beam parameters like beam current, energy and fluence constant. Now we are focusing on the mechanism taking place during the high energy ions and materials interaction. Such mechanism need to be explored in detail in order for better understanding and observation of radiations produced. The tuning of emitted radiation is also an important ingredient of our study.

Faculty associated: H.K. Malik

Microwave plasma interaction

We proposed to employ special kinds of microwave pulses for particle acceleration in plasma filled waveguide and also creating density gradient in plasma in particular direction. We have suggested important methods to divert and collect the accelerated particles from the waveguide. Based on the proposal, the cost of the particle accelerator can be brought down compared to the laser based accelerator systems. The microwaves are now being employed for the density modification which could be used for the resonant excitation and tuning of THz radiation and on the other side in fusion related aspects. Experimental studies related to controlling the density gradient in plasma by microwaves are also underway.

Faculty associated: H.K. Malik

Propagation, reflection and transmission of solitons:

We have developed theoretical models for the propagation, reflection and transmission of electrostatic solitons in different kinds of plasmas. For this, various transformations have been discovered in order to solve the relevant equations. Simulation study has been recently conducted for uncovering the role of perturbing pulse for the excitation of electromagnetic solitons and their collisions. Investigations are underway to find the conditions for total reflection keeling in mind the application of solitons in communications as well.

Faculty associated: Amita Das

Fast Ignition (FI) concept of laser Fusion

Fast Ignition (FI) concept of laser Fusion: The inertial confinement fusion scheme relies on achieving the Lawson criteria for fusion by working with a compressed high density fusion target of super-solid densities. While compression of fusion target by lasers is possible, the creation of a hot spot for ignition has simultaneously has been a problem. The fast ignition concept of laser fusion separates the task of compression and creation of a hot spot for ignition. This has several advantages as one no longer has to compress a hot fuel and nor does one have to deal with certain hydrodynamic instabilities which mix up hot and cold fluids. This is avoided in FI scheme of laser fusion where the electrons generated by a fast sub-picosecond laser pulse is utilized to create a hot ignition spot. The energetic electron transport through plasma and possible anomalous behavior of transport are crucial in this regard which are issues for investigation. One important study involved a proposal for a new mechanism of shock dissipation which was experimentally verified by groups in ILE Osaka and TIFR.

Faculty associated: H.K. Malik

Magnetic field generation and turbulence in laboratory plasmas

Issues related with magnetic field generation and their turbulence in laboratory laser plasma interaction having astrophysical implications are being studied. There are ongoing collaboration with TIFR experimental group of UPHILL laboratory.

Faculty associated: Amita Das

Research at the optics and photonics division of department of physics covers a wide range of topics, including nonlinear optics, quantum optics, nanophotonics, ultrafast optics, quantum technologies, biophotonics, singular optics, integrated optics, spectroscopy, optical fibre communication, holography, imaging, microscopy.and computational optics. The research activities are summarized under the following thematic areas of research:

Optical waveguides and photonic crystals

IIT Delhi Physics department has historically made important contributions to computational methods for electromagnetic wave propagation in optical waveguides (optical fibers and integrated optical devices). The work has important applications to optical communication, plasmonic sensors, and a number of opto-electronic devices and components. The faculty in this area are engaged in both theoretical work as well as experiments. The research on photonic crystals has led to novel multiple beam interference based techniques for development of photonic devices.

Faculty associated: Anurag Sharma, Arun Kumar, M R Shenoy, B D Gupta, R K Varshney, Joby Joseph, Vishal Vaibhav

Information Photonics

The research in this area has been devoted to holography, multilens imagers, integral imaging, extended depth-of-focus imaging, optical metrology and techniques for optical encryption/cryptography. The work in this area has applications to design of optical systems and computational algorithms for evolving novel imaging or display systems as well as optical security and data storage.

Faculty associated: oby Joseph, D S Mehta, P. Senthilkumaran, Aloka Sinha, Kedar Khare, Vishal Vaibhav

Biophotonics

The research in this area focuses on bio-medical optical imaging systems including a number of microscopy modalities (quantitative phase, fluorescence, super-resolution), Optical Coherence Tomography, spectroscopy, Fourier ptychography, etc. The faculty in this group has collaborations with leading medical schools/hospitals and have been working on developing novel diagnostic tools for clinical practices. Additionally collaborative research work in this area spans other diagnostic imaging modalities such as MRI, X-ray CT, etc.

Faculty associated: P K Gupta, Dalip Singh Mehta, Joby Joseph, Kedar Khare

Singular optics and optical coherence

The work on singular optics spans generation and propagation effects associated with exotic states of light such as optical vortices having orbital angular momentum and polarization singularities. Applications of this work include optical tweezers and novel beam engineering approaches for robust propagation through random media. Ongoing research in the department also includes fundamental investigatons on coherence and polarization of optical fields.

Faculty associated: P. Senthilkumaran, D S Mehta, Joby Joseph, Kedar Khare, Bhaskar Kanseri

Ultrafast optics

Research in this area is concerned with use of ultrafast lasers (femtosecond) for applications in material science, non-linear optics, lithography, tera-hertz generation etc. The department hosts a major DST-FIST facility on ultrafast optics and has state of the art instrumentation enabling collaborative work across the institute.

Faculty associated:G V Prakash, Sunil Kumar, Amartya Sengupta

Quantum photonics

The research on quantum photonics includes topical areas such as quantum information and communication, quantum key distribution, entaglement and squeezing, efficient downconversion in waveguides, quantum state tomography, light-matter interaction, all-optical devices and novel light sources.

Faculty associated:Bhaskar Kanseri, Joyee Ghosh, Vivek Venkataraman