07-01-2008 At 04:00:00 PM
Speaker: Dr. J.K. Tripathi, Institute of Physics
Category: Seminar of General Interest
Venue: Lecture Hall
In recent years, it has been shown that magnetic properties ofultrathin magnetic multilayers depend strongly on the surface andinterface structure, chemical composition, crystallinity, and grain sizesand their distributions. In general, all these structural properties canbe tuned by ion irradiation. In addition, it has been shown that themagnetic properties can also be tuned by ion irradiation. In this seminar,I shall talk on tuning the magnetic properties of ultrathin magneticmultilayers by ion irradiation
08-01-2008 At 04:00:00 PM
Speaker: S. Chandramohan, Kongunadu Arts & Science College, Coimbatore
Category: Seminar of General Interest
Venue: Lecture Hall
The effect of Swift Heavy Ion (SHI) irradiation on semiconductor materialsand devices is of significance both from fundamental as well asapplication aspects. Interesting phenomena like phase transformation incrystalline solids, sputtering of target material, surface and interfacemorphological changes, modification of optical band gap, etc have beenreported on thin films of metals/semiconductors. The II-VI compoundsemiconductors such as CdTe and CdS are widely studied for their provenapplications in optoelectronic devices such as solar cells, detectors,light emitting diodes, etc. Since the properties have strong dependence onthe preparation conditions and post deposition treatments, interest on themodification of thin film properties with the aid of novel techniques hasincreased. In this constitution, the successful exploitation of SHIirradiation to induce modifications in the properties of CdTe and CdS thinfilms has been studied. The evaporated films of CdTe and CdS wereirradiated with 100 MeV silver and 80 MeV oxygen ions and the propertieswere studied by X-ray diffraction, scanning electron microscopy (SEM),atomic force microscopy (AFM), optical absorption/transmittance,photoluminescence, and X-ray photoelectron spectroscopy. Upon irradiation,most of the important properties such as grain size, stress, optical bandgap, electronic structure, and native defects show significant changes
09-01-2008 At 04:00:00 PM
Speaker: Prof. Paolo Milani, Interdisciplinary Centre for Nanostructured Materials and Interfaces(CIMAINA) a
Category: Special Colloquium
Venue: Lecture Hall
Gas phase nanoparticle production, manipulation and deposition is of primary importance for the synthesis of novel nanostructured systems and for the development of industrial processes based on the convergence of micro- and nanofabrication. I will present and discuss an approach, based on supersonic cluster beam, introducing cluster sources, nanoparticle particle formation and growth mechanisms and the use of aerodynamic focusing methods that are coupled with supersonic expansions to obtain high intensity cluster beams with a control on nanoparticle mass and spatial distribution. The relevance of this approach for fundamental research and applications will be highlighted
14-01-2008 At 04:00:00 PM
Speaker: Prof. M.B. Paranjape, Univ. of Montreal, Canada
Category: Seminar of General Interest
Venue: Lecture Hall
We formulate the Josephson effect in a field theoretic language whichaffords a straightforward generalization to the non-abelian case. Ourformalism interprets Josephson tunneling as the excitation of pseudo-Goldstone bosons. We demonstrate the formalism through theconsideration of a single junction separating two regions with apurely non-abelian order parameter and a sandwich of three regionswhere the central region is in a distinct phase. Applications tovarious non-abelian symmetry breaking systems in particle andcondensed matter physics are given.
18-01-2008 At 04:00:00 PM
Speaker: Prof. N. Gisin, Univ. of Geneva, Switzerland
Category: Colloquium
Venue: Lecture Hall
Quantum communication is the art of transferring quantum states from one place to another. The most fascinating example is Quantum Teleportation: an object dissolves here and reappears there without ever existing at any intermediate location. In the first half of this presentation we present the experimental challenges that had to be overcome in order to demonstrate teleportation from our lab to a Swisscom center downtown Geneva. In the second half we discuss some conceptual issues of quantum nonlocality. We consider it both from the point of view of the resources required to simulate it and as a resource enabling one to achieve tasks otherwise impossible
18-01-2008 At 02:30:00 PM
Speaker: Prof. K. Vishwanathan, Simon Frazer University, Canada
Category: High Energy Group Seminar
Venue: Lecture Hall
07-02-2008 At 04:00:00 PM
Speaker: Prof. Narayan Pradhan, IACS, Kolkatta
Category: Seminar of General Interest
Venue: Lecture Hall
High-temperature solution phase synthesis of different nanomaterials through bottom up approach would be presented. Synthesis of well studied quantum dots and doped nanocrystals in different solvent medium would be focused as model system. Our recent works on oriented attachment and formation of different complex nanostructures through ligand manipulation would be discussed.
08-02-2008 At 04:00:00 PM
Speaker: Rahul Marathe, Raman Research Institute, Bangalore
Category: TPSC Seminar of General Interest
Venue: Lecture Hall
12-02-2008 At 04:00:00 PM
Speaker: Prof. S.K. Bhattacharya, PRL, Ahmedabad
Category: Seminar of General Interest
Venue: Lecture Hall
Stable isotopes of hydrogen, carbon, nitrogen and oxygen are present in significant amounts in all the natural materials. However, their abundances are not invariant. The natural variations in stable isotopes of a given element can arise due to many factors and some of these are tractable through theoretical calculations. The change in isotope content of an element from one phase/compound to another is termed as fractionation. There are two basic mechanisms of fractionation—kinetic and equilibrium which can be linked to the nature of the associated reactions.The variations in the natural materials can be used to trace the processes undergone by these systems. Various environmental issues like pollution, global warming, changes in ocean productivity, tracing pathways of carbon cycle etc., can be addressed by measurement of the stable isotope ratios in the relevant materials. This talk will give an introduction to this subject as well as discuss some recent discoveries in this area.
14-02-2008 At 04:00:00 PM
Speaker: Prof. P.Mitra,SINP, Kolkata
Category: TPSC HEP Seminar
Venue: Lecture Hall
19-02-2008 At 04:00:00 PM
Speaker: Prof. T. Tatsumi, Kyoto University, Japan
Category: Seminar of General Interest
Venue: Lecture Hall
21-02-2008 At 04:00:00 PM
Speaker: Prof. Sarira Sahu, Institute de Ciancias Nuocleares, Universidad Nacional Autonoma de Mexico, Mexico
Category: Seminar of General Interest
Venue: Lecture Hall
The long and short gamma-ray bursts are believed to be produced due tocollapse of massive stars and merger of compact binaries respectively.All these objects are rich in neutron and the jet outflow from these objectsmust have a neutron component in it. By postulating the neutron, anti-neutron oscillation in the gamma-ray burst fireball, we show that, 19-38 GeV neutrinos and anti-neutrinos can be produced due to annihilation of anti-neutrons withthe background neutrons. Observation of these neutrinoswill shed more light on the nature of the GRB progenitors and also be aunique signature of physics beyond the standard model. Apossible way of detecting these neutrinos in future is also discussed.
26-02-2008 At 04:00:00 PM
Speaker: Prof. Sachindfo Vaidya, IISc., Bangalore
Category: TPSC HEP Seminar
Venue: Lecture Hall
We outline recent advances in the quantization of noncommutativequantum field theories that preserve spacetime symmetries. This novelquantization procedure (called twisted quantization) has phenomenologicalimplications, as well as consequences for model-building in particlephysics. We explain some of these effects, like the deformation of usualspin-statistics connection at high energies.
28-02-2008 At 11:00:00 AM
Speaker: Dr.Sumati Surya, RRI, Bangalore
Category: TPSC HEP Seminar
Venue: Lecture Hall
In the causal set approach to quantum gravity, the spacetimecontinuum is replaced by a discrete substructure, the causal set, which isa locally finite poset. I will spend the first half of the talk with ageneral introduction to causal set theory. I will then discuss a 2D modelof causal set quantum gravity which overcomes the so-called entropy problemassociated with quantum geometries. In particular, 2D Minkowski spacetimeis a prediction of the theory in the large volume limit.
03-03-2008 At 04:00:00 PM
Speaker: Navinder Singh, IOP
Category: Condensed Matter Group Seminar
Venue: Lecture Hall
We extend Tooru-Cohen analysis for nonequilirium steady state(NSS) of aBrownian particle to nonequilibrium oscillatory state (NOS) of Brownianparticle by considering time dependent externaldrive protocol. We consider an unbounded charged Brownian particle in thepresence of oscillatingelectric field and prove work fluctuation theorem, which is valid for anyinitial distribution and at alltimes. For harmonically bounded and constantly dragged Brownian particleconsidered by Tooru andCohen, work fluctuation theorem is valid for any initial condition(alsoNSS), but only in large timelimit. We use Onsager-Machlup Lagrangian with a constraint to obtainfrequency dependent workdistribution function, and describe entropy production rate and propertiesof dissipation functionsfor the present system using Onsager-Machlup functional.
17-03-2008 At 04:00:00 PM
Speaker: Professor T.P.Singh, TIFR, Mumbai
Category: Colloquium
Venue: Lecture Hall
18-03-2008 At 04:00:00 PM
Speaker: Prof. Partha Guha, S.N. Bose Centre, Kolkata
Category: Seminar of General Interest
Venue: Lecture Hall
20-03-2008 At 04:00:00 PM
Speaker: Dr. Gagan Bihari Mohanty, SLAC, USA
Category: Seminar of General Interest
Venue: Lecture Hall
Study of B meson decays to hadronic final states without a charm quarkprobes the dynamics of both weak and strong interactions, and thereforeplays a key role in understanding the charge-parity (CP) violation andlow meson spectroscopy. In this talk, I shall discuss recent results oncharmless hadronic B decays, studied using data collected with the BABARdetector at the PEP-II asymmetric-energy e+e- collider at the StanfordLinear Accelerator Center. Future prospects for this exciting branch offlavour physics at the proposed Super B Factory will also be discussed.
24-03-2008 At 04:00:00 PM
Speaker: Dr. B. Dey, University of Pune, Pune
Category: TPSC Seminar
Venue: Library Lecture Hall
26-03-2008 At 04:00:00 PM
Speaker: Dr. Rama Panda, IIT, Kharagpur
Category: Seminar of General Interest
Venue: Lecture Hall
21-04-2008 At 04:00:00 PM
Speaker: Prof. V. Ravishankar, Physics Dept. I.I.T. Kanpur
Category: Particle/Nuclear Physics Seminar
Venue: Lecture Hall
We analyze a class of hot EOS which have been proposed recently within the improved pQCD framework, and show how their predictions can be checked in heavy ion collisions.
22-04-2008 At 04:00:00 PM
Speaker: Prof. V. Ravishankar, Physics Dept. I.I.T. Kanpur
Category: Seminar of General Interest
Venue: Lecture Hall
A complete characterization of a two qubit mixed state entanglementis provided, of which measures such as concurrence arise as particularbenchmarks. As an application, the role of entanglement in NMR quantumcomputation is resolved and clarified.
23-04-2008 At 04:00:00 PM
Speaker: Prof. M.P. Das, The Australian National University, Australia
Category: Seminar of General Interest
Venue: Lecture Hall
Kohn anomaly (KA) occurs in normal metals, observed as a kink in the phonon dispersion. Recently it has been observed in superconductors by inelastic neutron scattering with a surprise that the frequency of KA is twice the pair binding energy. Does this result raise any question on our understanding of standard model of conventional superconductors?
22-05-2008 At 04:00:00 PM
Speaker: Prof. R. Sahadevan, Madras University
Category: Seminar of General Interest
Venue: Lecture Hall
17-06-2008 At 04:00:00 PM
Speaker: Dr. V. Rama Rao, Post Doc., IOP
Category: Seminar of General Interest
Venue: Lecture Hall
Photoemision spectroscopic results obtained on (a)CaB6 and LaB6(b)PdAg(100) surface allys (c) Ta/Si(100) and (d) Ta nano-structures willbe discussed. CaB6 exhibits surprisingly a ferromagnetic behavior withoutmagnetic ions present. Origin of the FM behavior observed in CaB6 wasinvestigated using high resolution photoemission studies. A pseudogapformation has been observed in LaB6 which explains the low temperatureanomalies exhibited by LaB6. Core level chemical shifts observed onPdAg(100) ordered surface alloys will be discussed against the core levelchemical shifts observed for random bulk PdAg alloys. Thermal stability ofTa2O5 deposited on Si(100) was investigated using high energyphotoemission technique. The effect of in-situ annealing on the corelevels of Ta, Si and O will be discussed briefly. Ta nano-structures havebeen prepared by sputtering Ta foil in-situ in XPS machine using argon ionsputtering. Ta 4f exhibited a surface core level shift of 0.5 eV with anegligible bulk Ta 4f intensity. High intensity of the surface core levelindicates nano-structureformation and AFM topography shows nano-structure formation.
29-07-2008 At 04:00:00 PM
Speaker: Dr. Sanjay Gupta (BITS, Mesra)
Category: TPSC Seminar
Venue: Lecture Hall
This work concerns the interplay of strong correlation and disorder in two dimension at half-filling using 2D t-t' Hubbard modelwith deterministic disorder. Inclusion of t' leads to a metallic phase at half-filling below a certain critical value of U. Above this critical value Uc correlation favours Neel ordering while disorder alone leads to double occupancy over the lower energy site. This competition leads to the emergence of a metallic phase, which has been quantified by the calculation of Kubo conductivity, gap at half-filling, density of states, spin order parameter and bandwidth calculation. The deterministic disorder follows a Fibonacci sequence. We have also studied the effect of reducing the dimension of the system. Calculation for both zero and finite temperatures have been done.
04-08-2008 At 04:00:00 PM
Speaker: Prof. Sanjay Kumar Swain, SLAC/ Stanford University
Category: Seminar of General Interest
Venue: Lecture Hall
12-08-2008 At 04:00:00 PM
Speaker: Dr. Abu Mohd. Pharhad Hussain,Dept. of Physics, Gauhati University, Guwahati.
Category: Seminar of General Interest
Venue: Lecture Hall
Conducting polymer is a very interesting and scientifically as well astechnologically important class of polymer. This research work aims togain an insight into the monomer level processes and mechanism ofelectropolymerization of conducting polymer (CP) so as to control theporosity and morphology and standardize various parameters for obtainingbetter quality CP films. Another objective is to study the effects ofheavy ion irradiation on CP electrodes and to understand the interactionof the fast ions with the polymer film. Polyaniline, polypyrrole andpoly(3-methylthiophene) CP films doped with different dopants have beeninvestigated. Electrochemical synthesis of CP films was carried out in three electrodesingle compartment electrochemical cell on indium doped tin oxide (ITO)coated glass substrates. These CP films were irradiated with swift heavyion (SHI) beam of 160 MeV Ni12+ and 120 MeV Si9+ to investigate theeffect of irradiation on CP electrodes. Cyclic voltammetry, dcconductivity, XRD, SEM, UV-Vis and FTIR studies were carried out forcharacterization of the CP films before and after irradiation. Theperformance of the CP films as electrodes has also been investigated byfabricating supercapacitors with unirradiated and irradiated CP films aselectrodes.The electrochemical polymerization of CP produces better quality films inthe potentiodynamic mode as compared to potentiostatic mode. The dcconductivity of the conducting polymer films has been observed to bedependent on the type of dopant ions. The scanning electron microscopy ofthe conducting polymer films shows that the potentiodynamic polymerizationmethod produced films with better surface morphology as compared to thoseby the potentiostatic method. Grain growth and densification of thepolymer film surface have been observed upon SHI irradiation. The UV-Visstudy showed that the polymer absorbing at higher wavelength exhibitsbetter conductivity. Increase in carrier absorption intensities with shiftof absorption peaks towards higher wavelength were observed in the UV-Visspectra of the irradiated CP films indicating lowering of band gap andincrease in electrical conductivity. The dopant ion interaction absorptionpeaks in the FTIR spectra confirmed the presence of the dopants in the CPfilms deposited by electrochemical polymerization and also afterirradiation. The XRD patterns of the unirradiated CP films showedsemi-crystalline nature of the films with increase in degree ofcrystallinity upon SHI irradiation.Solid state all-polymer redox supercapacitors fabricated using CP films aselectrodes and PVDF-HFP-PMMA gel polymer electrolyte showed goodcapacitive behaviour with capacitance on the order of 200-250 F/gm andCoulombic efficiency of about 90-96%. Stability tests up to 10,000charge-discharge cycles showed that the supercapacitors fabricated byusing SHI irradiated CP films exhibit slightly less capacitance andCoulombic efficiency but markedly improved electrochemical stability. Avery small decrease in internal resistance of the supercapacitors is foundafter SHI irradiation. A decrease in total charge-discharge time has alsobeen observed for supercapacitors with SHI irradiated electrodes.
19-08-2008 At 04:00:00 PM
Speaker: Dr.Shamik Gupta, TIFR, Mumbai
Category: TPSC Seminar
Venue: Lecture Hall
Driven diffusive systems are generically out of equilibrium. Iwill consider two paradigmatic examples, the asymmetric simple exclusionprocess and the zero-range process. I will discuss size effects on thebehavior of fluctuations in the nonequilibrium stationary state of these twoprocesses on a one-dimensional periodic lattice of finite size. Theexclusion process involves hard core particles executing biased diffusionwith a constant rate. In the zero-range process, particles perform biasedhopping between sites with a rate which depends on the occupancy at thedeparture site. In the stationary state, this process shows a phasetransition as a function of the particle density, from a low-densitydisordered phase to a high-density condensed phase. In both these processes,size effects interplay with the nonequilibrium dynamics to bring in richdynamical phenomena otherwise absent in equilibrium.
20-08-2008 At 03:30:00 PM
Speaker: Dr. Dipak Munshi, Cambridge University.
Category: Seminar of General Interest
Venue: Lecture Hall
15-09-2008 At 04:00:00 PM
Speaker: Prof. Gautam I. Menon,The Institute of Mathematical Sciences, Chennai
Category: Colloquium
Venue: Lecture Hall
Pine, Chaikin and collaborators [Nature (2005), Nature Physics (2008)]have recently studied the transition between reversible andirreversiblebehavior in a simple experiment. The experiment consists of observingand studying the trajectories of a large number of particles suspendedina fluid sheared between two coaxial cylinders. These experimentsillustrate a novel way in which a driven many-particle system canself-organize (termed``random organization'' by these authors). They also illuminateseveral problems which lie at the foundations of statisticalmechanics, such as theconnection between irreversible behaviour at the macroscopic scale andmicroscopic reversibility at the microscale.I will first describe these experiments and then present a simplemodel for the underlying physics. Predicting universal features of thereversible-irreversibletransition seen in these experiments then becomes possible. Thesepredictions are in reasonable agreement with what is seen in theexperiments. I will also brieflydescribe the connection to recent ideas concerning the ``jamming''transition in granular materials, ideas that may have broaderimplications for theories of the glasstransition.
16-10-2008 At 04:00:00 PM
Speaker: Gowri Manickam, Dept. of Applied Molecular Physics, Roadboud University Nijmegan, The Netherlands
Category: Condensed Matter Seminar (Experimental)
Venue: Lecture Hall
Our highly industrialized society is always in search of ways to reduce or control friction and wear of materials. Diamond coatings can provide an efficient solution for these problems. The focus of this research work is to study the potential of diamond coatings to improve the tribological properties of steel components. Although chemical vapour deposition (CVD) of diamond is well researched and well established on various non-diamond substrates, deposition on ferrous materials is difficult to obtain and not yet up to the stage of commercial realization. One of the main challenges associated is that iron comes under the group VIII transition metals and due to their partially filled 3d orbital, Fe atoms are highly reactive towards carbon. On the other hand, carbon also has a high coefficient of diffusion in the iron matrix. As a result, the incubation time to reach the critical carbon concentration is very long for steel substrates. Another major drawback is the thermal expansion coefficient mismatch between steel and diamond, which results in high thermal stresses upon cooling, leading to poor adhesion. Using various interlayer and surface pretreatment techniques, we have overcome the above mentioned problems and successfully obtained diamond coatings on steel substrates by hot filament chemical vapour deposition (HFCVD) technique. Tribological characterization of the diamond coated steel substrates was performed under small amplitude oscillatory motions, known as fretting. In this talk, an overview of the diamond CVD mechanism, challenges, interlayer systems and the fretting wear behaviour of the diamond coatings will be presented.
24-10-2008 At 04:00:00 PM
Speaker: Brajesh Chandra Choudhary (University of Delhi)
Category: Seminar of General Interest
Venue: Lecture Hall
For last couple of months the story of the Large Hadron Collider (LHC), its success,its perceived failure and associated fear has permeated both the popular and the scientific news. In some quarters while it is being touted that the LHC will answer all the possible mysteries of the Universe, in another section of press it is being said that the LHC will eventually lead to the destructionof the Universe.In this talk I will present the status of the Large Hadron Collider (LHC)machine at the European Organization for Nuclear Research (CERN), Geneva,Switzerland and one of the the two multipurpose detectors, the Compact MuonSolenoid (CMS) meant to record proton-proton collision at a center of massenergy of 14 TeV. I will also give a brief review of first physics resultsthat are expected with the CMS detector at the LHC.
07-11-2008 At 04:00:00 PM
Speaker: Prof. Monique Combescure, Institut de Physique Nucleaire and University of Lyon, France
Category: Seminar of General Interest
Venue: Lecture Hall
We consider a quantum system of non-interacting fermions at temperature T in the framework of linear response theory. We show that semi-classical analysis is an appropriate framework to describe some of their thermodynamic properties, in particular through asymptotic expansions in the Planck constant of the dynamical susceptibility. We show how the closed orbits of the classical motion in phase space manifest themselves in these expansions, in the region of low temperature.
10-11-2008 At 04:00:00 PM
Speaker: Prof. Jean-Marc Richard, Universite Joseph Fourier and IN2P3, Grenoble, France
Category: Seminar of General Interest
Venue: Lecture Hall
We review the long-standing arguments in favor of stable exotic mesons with two heavy quarks and two light antiquarks. For a flavor independent interaction, as suggested by QCD, this mass configuration is favored as compared to equal-mass or hidden-charm configurations, in complete analogy with the pattern observed in atomic physics when the hydrogen molecule is compared to the positronium molecule or to the hydrogen-antihydrogen system.We then present the results of a recent model calculation, inspired by the strong coupling limit of QCD: the linear potential for a quark-antiquark pair in mesons is generalized as a Y-shape interaction for baryons and a Steiner tree for tetraquarks. The four-body problem is then solved by an accurate variational method. An analytic upper bound is also obtained, which confirms the numerical results in the limit of large values for the quark mass ratio.
10-11-2008 At 11:00:00 AM
Speaker: Dr.Nathalie Herlin Boime, CEA, Sacley, France
Category: Seminar of General Interest
Venue: Lecture Hall
17-11-2008 At 04:00:00 PM
Speaker: Prof. R. Shrianand, IUCAA, Pune.
Category: Colloquium
Venue: Lecture Hall
Our understanding of orgin of the universe is mainly in frame work of Big-Bang models. Stringent constraints on these models come from light element abundances and thermal evolution of cosmic microwave background. Development of structures in the Universe very much depends on the mass density of different components and their redshift evolution.Development of fundamental physics relies on the constancy of various fundamental quantities such as the fine structure constant. Detecting or constraining the possible time variations of these fundamental physical quantities is an important step toward a complete understanding of basic physics.High quality absorption lines seen in the spectra of distant QSOs allow one to address all the above listed issues. In this talkwe will present the overview of the approach and highlightsome very recent results based on observations taken with VeryLarge Telescope (VLT) in Chile and Giant meterwave radio telescopenear Pune.
21-11-2008 At 04:00:00 PM
Speaker: Prof. R. Suryanarayanan University of paris-sud Orsay, France
Category: Seminar of General Interest
Venue: Lecture Hall
Physicists and chemists have been interested in devising materials and methods to induce ferromagentic order in several oxides. Such studies provide an understanding of the fundamental mechanisms involved. In addition, these materials are candidates for potential applications in magnetic memories, sensors etc. Typical examples are ferrites and garnets. However there are other oxides which show novel properties. In this talk, I will describe three such classes of materials - double layer spin cluster glass manganites that exhibit a resistance drop of 1 million in moderate fields but at low temperatures, frustrated pyrochlores where ferromagentic order is induced by proper selection of substitution and undoped indium oxide in which charge carriers seem to be spin polarized.
08-12-2008 At 04:00:00 PM
Speaker: Prof. S,D. Mahanti, Deapartment of Physics and Astronomy, Michigan State University, East Lansing, M
Category: Colloquium
Venue: Lecture Hall
Thermoelectrics (TE) are solid state systems which convert heat toelectricity or do active cooling by passing a current through it. They canbe used for power generation or cooling devices. Although TE have been around for more than 100 years they are not widely used because of theirlow efficiency. The efficiency of a TE is determined by a dimensionlessfactor ZT called the figure of merit which depends on both electronic andphononic properties of the solid. Due to competing physical effects it hasbeen very difficult to make ZT much larger than 1. However, in recentyears several theoretical ideas (electron crystal phonon glass, transportin reduced dimensionality, dissipation-less energy transport throughenergy filtering etc ) have been proposed to increase ZT beyond 1. Severalof these ideas have been implemented in designing novel materials and someof these show a ZT value ~2. These concepts and how they operate in thesematerials will be discussed. Conditions for dissipation-less energytransport which occurs in a perfect thermoelectric will be explained.Attempts to design such materials will be described.* Work partly supported by a ONR-MURI grant.
17-12-2008 At 04:00:00 PM
Speaker: Dr. Dipak Kumar Goswami, IIT Guwahati, Guwahati – 39, Assam
Category: Seminar of General Interest
Venue: Lecture Hall
In the last decade there has been increased emphasis on crystallizingpolymers or assembling small organic molecules to form well orderedorganic films. There are many polymers which can not be crystallized bystandard methods that protein crystallographers use. We have demonstrateda technique that has possibility to be used as a tool to crystallizecertain molecules. On the other hand, the development of the field oforganic electronics has benefited from the unique set of characteristicsoffered by π-conjugated oligmoers and polymers. These molecules showsemiconducting properties. Remarkable progresses have been made on thedevelopment of the devices based on organic semiconducting (OSE)materials due to the unique capabilities offered by the tunability andsynthesis of organic molecules together with the possibility of low-costand large area fabrication at moderate substrate temperature. Some fieldsof applications are organic thin-film transistors (OTFTs), organiclight-emitting diodes (OLEDs), photovoltaic cells etc. Though themobility of the OSE thin films are relatively lower than that ofinorganic counterparts like Si or Ge but highly ordered films canimprove mobility and demonstrated performance of organic thin filmtransistors (OTFT) based on these ordered films suggest that they arecompetitive candidates for replacing the existing or novel thin filmtransistors applications requiring large-area coverage, structuralflexibility, low temperature processing. In this talk I am going todiscuss how to assemble OSE molecules to grow well ordered organicfilms which show improved device properties. Nevertheless, there are manyopen questions and challenges related to the understanding the growthmechanisms and physical principles of molecular ordering in the organicfilms.
22-12-2008 At 04:00:00 PM
Speaker: Dr.B. Chandrasekhar. IFT. Sao Paulo
Category: HEP (Theory ) Seminar
Venue: Lecture Hall
24-12-2008 At 04:00:00 PM
Speaker: Dr. Prafulla Kumar Behera, Stanford University
Category: HEP (Experimental) Seminar
Venue: Lecture Hall
26-12-2008 At 04:00:00 PM
Speaker: Dr. S. Chowdhury, Department of Physics, Gauhati University, Guwahati, Assam-781014, India
Category: Seminar of General Interest
Venue: Lecture Hall
Swift Heavy Ion (SHI) irradiation of semiconductor nanostructures is arapidly developing area of nanomaterials research which resultssignificant changes in structural and physical properties of such lowdimensional systems. The present study describes SHI irradiation effect onbare and silica (SiO2) coated semiconductor nanoparticles embedded ininsulating polymer (polyvinyl alcohol) and on a composite of semiconductornanoparticles and conductingpolymer(2-methoxy-5-(2-ethyl-hexyloxy)-pphenylene vinylene). The nanosemiconductor samples of PbS, CdS and ZnS were prepared following aninexpensive chemical route. Characterizations of the samples were carriedout with X-ray diffraction, optical absorption spectroscopy,photoluminescence and transmission electron microscopy. The UV–Visabsorption spectra reveal blue shift relative to bulk material inabsorption energy while PL spectra suggest that surface state and nearband edge emissions are dominating in case of bare and coated samplesrespectively. The samples were irradiated with 160 MeV Ni-ion beam withfluences in the range of 1e12 to 1e13 ions/cm2. The investigation afterSHI irradiation showed fluence dependent luminescence behavior and sizeenhancement of bare nanoparticles while reduction of particle size wasobserved in the composite system. However, coated samples exhibit betterstability upon SHI irradiation compared to the bare one.
29-12-2008 At 04:00:00 PM
Speaker: Prof. D.P. Roy, Homi Bhabha Center for Basic Education, TIFR, Mumbai.
Category: Colloquium
Venue: Lecture Hall
We have seen by now all the basic constituents of matter(quarks & leptons) along with the carriers of the basic forces (i.e.gauge bosons). But the story is not complete yet. A consistent theory of their masses requires the presence of Higgs bosons along with Supersymmetric particles, which we hope to discover at LHC. Discovery of theseparticles will also throw light on the nature of phase transition theUniverse went through a few picoseconds after its creation, and the nature of Dark Matter that permeates throughout the Universe today as a relic of that early history.
30-12-2008 At 04:00:00 PM
Speaker: Prof. X.Vinas, Department of Physics, University of Barcelona, Spain
Category: Colloquium
Venue: Lecture Hall
30-12-2008 At 04:00:00 PM
Speaker: Prof. X. Vinas, Department of Physics, University of Barcelona, Spain
Category: Colloquium
Venue: Lecture Hall