# List of Seminars

 Speaker: Dr. Sunil Kumar Affiliation: Weizmann Institute of Science, Israel Title: Contolled multiphoton micro-spectroscopy for high resolution imaging applications. Date: 22nd October, 2014 (Wednesday) Time: 11 am Venue: FB-382 Speaker: Dr. Sita Sunder Affiliation: Postdoc in Physics, IIT Kanpur Title: Flow shear driven instability in EMHD Date: 16 September 2014 Time: 4 pm Venue: Old corelab 103E Meeting Room Speaker: Sriram Guddala Affiliation: Metamaterials & Plasmonics Lab, Department of Physics, IIT Kanpur Title: Metal-Dielectric Periodic Photonic Structures Date: 27 August 2014 (Wednesday) Time: 3 pm Venue: FB - 382 Abstract: The optical field confinement in periodic metal-dielectric photonic structures has been of great interest to achieve intense localized electric field strengths due to unified properties driven from plasmonic properties of metallic nanostructures and photonic band gap properties of periodic dielectric structures [1]. Here, the metal-dielectric photonic crystals (MDPCs) and some preliminary results on metamaterial perfect optical absorbers be discussed. In the context of MDPCs, it will be shown that the confined optical fields resulted from redistributed photon density of states and their influence on enhancement of Raman scattering in metal nanoparticles impinged 3D (inverse opal structures) and 1D (multilayered microcavity) photonic crystals [2-3] . The intense optical fields are obtained on excitation of band edge (3D opals) and defect state (1D microcavity) photonic modes of photonic band gap structures and their coupling to the surface plasmon resonance properties of impinged metal nanoparticles. These intense optical fields were further probed by performing spectral and angle resolved surface enhanced Raman scattering (SERS) studies, and the enhancement of Raman scattering is understood through a novel photon-plasmon-phonon interaction mechanism. Our studies show a novel aspect of PBG influence to accomplish a highly reliable periodic metal-dielectric SERS substrate for sensing and photonic applications. At the end it will be discussed some of the recent studies on design, fabrication and characterization of novel architectures of multilayer metal-dielectric perfect optical absorbers for visible and NIR wavelengths. References: [1] S. Guddala, K. Shadak Alee, and D. Narayana Rao, "Fabrication of multifunctional SnO2 and SiO2-SnO2 inverse opal structures with prominent photonic band gap properties," Opt. Mater. Express 3, 407-417 (2013). [2] S. Guddala, V. K. Dwivedi, G. Vijaya Prakash and D. Narayana Rao, "Raman scattering enhancement in photon-plasmon resonance mediated metal-dielectric microcavity," Journal of Applied Physics, 114, 224309 (2013). [3] S. Guddala, K. S. Alee, A. Chiappini, M. Ferrari, and D. Narayana Rao, "Experimental investigation of photonic band gap influence on enhancement of Raman-scattering", Journal of Applied Physics, 112, 084303 (2012). Speaker: Dr. Ipsita Mandal Affiliation: Perimeter, Waterloo Title: Low Energy Physics of a Non-Fermi Liquid System Date: 20 August 2014 Time: 3 pm Venue: FB - 382 Abstract: We devise a renormalization group analysis for quantum field theories with Fermi surface to study scaling behaviour of non-Fermi liquid states in a controlled approximation. The non-Fermi liquid fixed points are identified from a Fermi surface in (m+1) spatial dimensions, while the co-dimension of Fermi surface is also extended to a generic value. We also study superconducting instability in such systems as a function of dimension and co-dimension of the Fermi surface. The key point in this whole analysis is that unlike in relativistic QFT, the Fermi momentum kF enters as a dimensionful parameter, thus modifying the naive scaling arguments. The effective coupling constants are found to be combinations of the original coupling constants and kF.

 Speaker: Prof. Sayan Kar Affiliation: IIT Kharagpu Title: Eddington-inspired Born-Infeld gravity Date: 27th March 2014, Thursday Time: 4 pm Venue: FB - 382
 Speaker: Dr. Sinu Mathew Affiliation: NUSNNI-NanoCore and Dept. of Electrical and Computer Engineering, National University of Singapore Title: The Effects of MeV Proton Irradiation on Interface Two-Dimensional Electron Gas (LaAlO3/SrTiO3) and Layered Solids (MoS2,graphene) Date: 3rd March 2014, Monday Time: 12:00 pm - 1:00 pm. Venue: FB - 382 Abstract: The two-dimensional electron gas (2DEG) formed at the interface between two band insulators LaAlO3 (LAO) and SrTiO3 (STO) is one of the most fascinating systems in the field of oxide research. Tailoring of the conductivity of this interface 2DEG is a challenge for the practical applications of this system. MeV Proton irradiation on LAO/STO system is found to manipulate interfacial conductivity by carrier localization and eventually producing an insulating ground state by tailoring the defect structure of the substrate STO. The results of electrical and magneto-transport, Raman spectroscopy and spectroscopic ellipsometry will be discussed[1]. The second part of the talk will be on the effects of MeV Proton irradiation on Molybdenum disulphide and graphene. MoS2 a diamagnetic layered solid, is found to show ferrimagnetic ordering at room temperature when exposed to 2 MeV proton beam[2]. A disorder mode corresponding to a zone-edge phonon and a valency of Mo higher than +4 have been detected in the irradiated samples. The stability of supported and suspended graphene under MeV Proton irradiation will also be discussed[3]. References S. Mathew, A. Annadi, T.K. Chan, Teguh Citra Asmara, D. Zhan, Ariando, A. Rusydi, Z.X Shen, M.B.H. Breese and T. Venkatesan. ACS Nano 7 (2013) 10572 S. Mathew, K. Gopinadhan , T.K. Chan, X.J. Yu, D. Zhan, L. Cao, A. Rusydi, M.B.H. Breese, S. Mathew, T.K. Chan, D. Zhan, K. Gopinadhan, A.R. Barman, M.B.H. Breese, S. Dhar, Z.X. Shen, T.Venkatesan and John TL Thong. Carbon 49 (2011) 1720; J. Appl. Phys. 110 (2011) 84309
 Speaker: P. Santhana Raman (Post-doctoral fellow at Institute of Physics, Bhubaneswar) Affiliation: Centre for Ion Beam Applications, Department of Physics, National University of Singapore, Singapore Title: Research and Development with Energetic Broad- and Nano- Ion Beams:From Ion Beam Analysis to Novel Materials Modification and Proton Beam Writing Systems Date: 24th February, 2014 (Monday) Time: 3:30 pm - 4:30 pm. Venue: FB - 382 Abstract: The process that can be accomplished using energetic ion beam technique broadens itself with no limit. Starting from routine materials analysis (via various Ion beam analysis technique), the advent of ion beam extends to carve and alter structures at nano scale, with nano-sized ion beam, to form novel materials. The cause and the effect of these energetic ion beams on both materials and soft-tissues are of paramount importance in understanding it in terms of both fundamental and application point of view. This talk will cover the Ion beam analysis techniques that were crucial in novel materials synthesis (especially with embedded InN and ZnO nanoclustres in silica matrix). The systematic approach, using energetic ion beams, in producing surface patterns will be discussed in the light of basic physics and its applications. Later in the talk I will introduce and explain about the next generation lithographic technique, namely Proton Beam Writing and its capability to produce high aspect ratio nanostructures. The developmental activities involved in making of high brightness ion source, to be used in next generation compact proton beam lithography, with a promise to deliver sub-10 nm beam spot size, will also be discussed.
 Speaker: Dr. Haraprasanna Lenka (Post-doctoral fellow at Institute of Physics, Bhubaneswar) Title: Microscopic characterization of GaN heterostructures using RBS/C and TEM: A comparative study. Date: January 16th, 2014 (Thursday) Time: 4:00 pm - 5:00 pm. Venue: FB - 382 Abstract: Recently, the success of the growth of high quality c-GaN layers on Si substrate has attracted considerable academic and commercial interest, because it can facilitate the integration of microelectronics and optoelectronics. But the large lattice and thermal mismatch between GaN and Si introduces a lot of dislocations which pose a major obstacle in the production of defect-free layers, much needed for device applications. Hence, material processing requires intermediate monitoring to quantitatively track the amount of defects formed during growth. Apart from measuring the critical characteristics like the dislocation density, a good estimation of strain and composition is also important for device optimization. To meet this challenge, ion channeling is a very attractive and a powerful technique because of its unique mass sensitivity to the type of defects separately (such as point defects, dislocations, stacking faults or defect clusters). Results of RBS/C will be presented as a fast and non-destructive technique to analyze the defect density and the elastic strain, two parameters which can potentially affect the device performance in comparison with TEM results.
 Speaker: Debanjan Chowdhury (Harvard University) Title: Unconventional phases of quantum matter Date: January 15th, 2014 (Wednesday) Time: 11:00 am - 12:00 pm. Venue: FB - 382 Abstract: Theorists have been studying unconventional states of quantum matter over the past few years and starting recently, experiments on such states have finally appeared, generating much excitement. I will describe experimental observations on high temperature superconductors and magnetic insulators and their influence on our theoretical understanding. In the first part of the talk, I will introduce the theory of quantum criticality in metals and apply it to the phase diagrams of the high temperature superconductors. I'll review some of the experiments on the iron pnictides, which point toward the possible existence of a quantum critical point underneath the superconducting dome and try to offer a partial explanation for some of the mysterious observations[1]. In the second part of the talk, I'll review some recent experiments on a kagome lattice anti-ferromagnet and argue that many of the observed features can be explained by the presence of fractionalized excitations in a quantum spin liquid[2]. [1] D. Chowdhury, B. Swingle, E. Berg and S. Sachdev, Phys. Rev. Lett. 111, 157004 (2013). [2] M. Punk, D. Chowdhury and S. Sachdev, Nature Phys. (to appear), 2014; arXiv:1308.2222.
 Speaker: Dr. Sanjay Kumar Mandal (NIT Agartala) Title: Multiferroic Composites for Magnetic Field Sensors. Date: December 9th, 2013 Time: 11:30 am - 12:30 pm. Venue: FB - 382 Abstract: Multiferroics with two or more ferroic (ferroelectric, ferro/ferri/anti-ferromagnetic, ferroelastic) orderings have attracted considerable attention in recent years. Single-phase multiferroics are rare and their magnetoelectric (ME) responses are either weak or occur at temperatures too low for practical applications. Ferromagnetic-piezoelectric composites, however, show strong ME coupling at ambient temperatures. The ME effect is a property mediated by elastic deformation. The composites show a rich variety of phenomena including giant low-frequency ME interactions. This presentation will focus on recent developments in the physics and applications of composite multiferroics. The discussion will include our work on functionally graded composites for use as ultra sensitive magnetic field sensors.
 Speaker: Dr. Aditya Kelkar (TIFR, Mumbai) Title: Ion collisions with molecules and Clusters Date: January 8th, 2014 (Wednesday) Time: 4:00 pm - 5:00 pm. Venue: FB - 382 Abstract: The description of the temporal and spatial evolution of systems of mutually interacting particles is of fundamental importance in atomic collision physics. Theoretically the difficulty of this task lies in the fact that the Schrödinger equation is not analytically solvable for more than two particle systems even when the underlying forces are precisely known. On the other hand collisions with photons and charged particles (electrons and heavy ions) have proved to be excellent tools to investigate the structural and dynamical properties of physical systems like atoms, molecules, clusters and solid surfaces etc. The dynamics can be studied in a wide range of Coulomb interaction strength and time scales by suitable choice of heavy ion beams, offering the opportunity to study a multitude of processes such as ionization and capture, radiative and non-radiative relaxation etc to coherence effects and collective behaviour in many body systems as well as bond formation and rearrangement in chemical reactions. In this talk I shall discuss the interaction of heavy ions with many body systems taking two examples from my research work. In the first part, I will describe collisions of highly charged heavy ions with fullerene C60 in the intermediate velocity (vp ~ 10 a.u.) range, focusing on the excitation of a collective surface plasmon mode known as Giant dipole plasmon resonance or GDPR. In this velocity range the dwell time of the projectile ion is ~10-17 seconds and the interaction can be treated in the perturbative regime. However, in collisions at very low energy (vp ~ 0.01 a.u.) the interacting particles have sufficient time for electronic rearrangement and bond formation leading to chemical reactions. In particular I will discuss the dynamics of a bimolecular nucleophilic substitution reaction between F - (anion) and CH3Cl in gas phase using velocity map imaging (VMI) technique.
 Speaker: Dr. Arijit Saha (University of Basel, Switzerland) Title: Novel Transport phenomena in hybrid junctions of Nanowires Date: January 7th, 2014 (Friday) Time: 2:45 pm - 3:45 pm. Venue: FB - 382 Abstract: In the first part of the talk I shall give a brief introduction to my field of research called "Mesoscale and Nanoscale Physics" highlighting the subfield of low dimensional systems with examples and experiments. In the next part, I shall talk about transport properties of hybrid superconducting junctions of one dimensional n a no wi r es (NW). In particular, I shall demonstrate possible scenarios for production of pure spin current through such junctions. I shall also show that (a) effects due to inclusion of electron-electron interaction induced back-scattering in the wire, and (b) competition between the charge transport via the electron and hole channels across the junction give rise to a non monotonic behavior of the sub gap conductance as a function of temperature. ln the last part of the talk I shall introduce NW in the presence of Rashba spin orbit interaction, uniform magnetic field, and spatially modulated magnetic field. Such fully gapped system can support fractional fermion (FF) bound states at the two ends of the NW. I shall discuss the transport and noise signatures of such FF bound states which has never been investigated so far in literature.
 Speaker: Dr. Jaivardhan Sinha (National Institute for Materials Science (NIMS), Tsukuba, Japan) Title: Perpendicular magnetic anisotropy and current induced effective field in Ta(N)|CoFeB|MgO Date: December 6th, 2013 Time: 12:00 pm - 01:00 pm. Venue: FB - 382 Abstract: Perpendicular magnetic anisotropy (PMA) originating from the interface in Heavy metal(Pt, Ta)|Ferromagnet(Co, CoFeB)|Oxide structure (Al2O3, MgO) is of great interest because of its potential application in spintronics based devices. The recent finding of spin-orbit torque (spin Hall spin torque) in these heterostructures [1,2] has increased its significance manifold as it allows one to manipulate magnetization direction using in-plane current. Solid understanding the role of Heavymetal|Ferromagnet interface and Ferromagnet|Oxide interface is essential for utilizing them in application. In this talk I shall discuss the Ta|CoFeB interface properties in Ta(N)|CoFeB|MgO and the current induced effective field likely generated due to spin Hall effect from Ta. In general, Ta is known for creating a magnetic dead layer when placed next to a magnetic layer. As the CoFeB layer thickness is of the order of 1 nm to obtain PMA, thus it is desirable to have negligible magnetic dead layer from the point of view of thermal stability. The effect of Nitrogen doping in Ta underlayer on interface anisotropy, magnetic dead layer thickness and current induced effective field will be also discussed [3]. References: [1] Junyeon Kim, Jaivardhan Sinha, Masamitsu Hayashi, M. Yamanauchi, S. Fukami, T. Suzuki, S. Mitani and Hideo Ohno, Nature. Materials. 12, 240 (2013).[2] L. Liu, C. F. Pai, Y. Li, H. W. Tseng, D. C Ralph, and R. A. Buhrman, Science 336, 555 (2012). [3] Jaivardhan Sinha et al, Appl. Phys. Lett. 102, 242505 (2013).
 Speaker: Dr. Shibabrata Nandi (Jülich Centre for Neutron Science & Peter Grünberg Institute) Title: Structure, magnetism and superconductivity in Fe-based superconductors Date: November 27th, 2013 Time: 11:30 am - 12:30 pm. Venue: L8 (LHC) Abstract: In iron-based high-temperature superconductors, magnetic fluctuations and magneto-elastic effects are believed to be important for the superconducting electron pairing mechanism. To gain insight into the interplay between the different ordering phenomena and the underlying couplings we studied the magnetic order and lattice distortion on AFe2As2 (A = Ca, Sr, Ba, Eu) single crystals by neutron and x-ray diffraction. High-resolution x-ray diffraction and neutron scattering measurements reveal an unusually strong response of the lattice and ordered magnetic moment to superconductivity in Co-doped BaFe2As2 . We propose that the coupling between lattice and superconductivity is indirect and arises due to the magnetoelastic coupling, in the form of emergent nematic order, and the strong competition between the magnetism and superconductivity. For the P-doped EuFe2As2 , coexistence between the ferromagnetism and superconductivity was observed and explained in terms of formation of a spontaneous vortex state.
 Speaker: Dr. Ajay Soni (School of Basic Sciences, IIT Mandi, Himachal Pradesh) Title: Nanocomposites of Layered Chalogenides for Thermoelectric Applications Date: November 26th, 2013 Time: 12:15 Pm - 1:15 pm. Venue: L9 (LHC) Abstract: Research in the field of thermoelectricity (TE) is full of outstanding ideas, the materials having properties of an electron-crystal-phonon-glass, such as rattling semiconductors, alloys, heterostructures, and bulk-nanocomposites have shown to be efficient TE materials. In this context, the nanocomposites of layered chalcogenides (Te and Se) and pnictogen (Bi and Sb) materials have been preferably studied for their high-performance TE properties arising due to layered structure and narrow band gap.1 The efficiency of the TE material is quantified by a dimensionless thermoelectric figure of merit, $ZT = S^2\sigmaT/\kappa$, where S is the Seebeck coefficient, $\sigma$ is the electrical conductivity, $\kappa$ is the thermal conductivity and T absolute temperature. Thus the interplay of the three physical parameters makes the problem very complex for TE materials. The research talk will focus on a novel class of solution grown Bi2Te3-xSex nanoplatelet composites (NPCs) having an enhanced thermoelectric properties2 , and the effects of the thermodynamic environment during spark plasma sintering.3For the case of NPCs, the grain boundaries and interfaces are playing important role such that the charge carriers and phonons couple in a unique fashion. The subtle understanding of the interface crystallization, grain growth and filtering of electron and phonons will be discussed. A brief notion on the family of layered materials and their technological aspects will also be emphasized. References: 1. Dresselhaus, M. S., Adv. Mater. 2007, 19, 1043-1053. 2. Soni, A.; Yanyuan, Z.; Ligen, Y.; Aik, M. K. K.; Dresselhaus, M. S.; Xiong, Q., Nano Letters 2012, 12 (3), 1203. 3. Soni, A.; Yiqiang, S.; Ming, Y.; Yanyuan, Z.; Ligen, Y.; Xiao, H.; Zhili, D.; Aik, M. K. K.; Dresselhaus, M. S.; Xiong, Q., Nano Letters 2012, 12 (8) 4305
 Speaker: Dr. A K Sinha (Centre-Director, UGC DAE Consortium for Scientific Research, Kolkata) Title: Manipulating Ions for Science & Technology Date: November 25th, 2013 Time: 04:00 pm - 05:00 pm. Venue: FB 382 Abstract: We manipulate photons to form a beam of laser which finds numerous applications. In a somewhat similar way, we manipulate fast moving ions to use them in a very wide spectrum of scientific studies.Many technologies emerge out of these.I will try to cover some of the examples from my work involving such ion manipulations. Then i will make an attempt to dwell on such ion manipulations and their use in the Ion Beam Complex at IITK.
 Speaker: Dr. Bholanath Pahari (IISc Bangalore) Title: Probing Microscopic Information of Complex Materials by Nuclear Magnetic Resonance Techniques. Date: November 21th, 2013 Time: 11:00 am - 12:00 noon. Venue: FB 382 Abstract: Solid-state nuclear magnetic resonance (NMR) spectroscopy is a powerful physical method widely applied in modern fundamental and applied science. The two most important modes of solid state NMR for obtaining local physical and chemical information are wide-line static NMR and high-resolution magic angle spinning (MAS) NMR. Applications of both NMR modes and their advantages for the investigation of different categories of complex material will be discussed. Present seminar targets following three different topics. 51V NMR studies to understand the nature of ground state and low-lying excitations in the integer spin chain (also known as Haldane chain) compound SrNi2V2O8. 75As NMR for the investigation of electronic and lattice properties of recently discovered iron arsenide high-temperature superconductor CeFeAsO1−xFx (TC ∼ 40 K). Multinuclear MAS NMR studies to understand the structure - property relationships in oxide-ion conducting materials of P − doped La2Mo2O9 .
 Speaker: Dr. Shirish Chodankar (SLS, Paul Scherrer Institut, Switzerland) Title: Hydration forces and ion-ion correlation in confined fluids revealed by X-ray Reflectivity Date: November 18th, 2013 Time: 11:30 am - 12:30 pm. Venue: FB 382 Abstract: When a liquid is confined within a nanometer-sized gap, the combination of interfacial effects and size often confer to the system properties much different from those observed in bulk fluids [1]. In particular, understanding the structure of electrolytes confined between two aluminium-phyllosilicates walls could be enlightening in a number of fields, ranging from biology to nuclear waste management, as well as clarify some fundamental issues regarding alkali hydration energies and their influence on the surrounding hydrogen bond network. We have adapted a surface force apparatus (SFA) [2] to be used as confinement device for two sets of X-ray reflectivity (XRR) experiments conducted at the cSAXS (XSA12) beamline of the Swiss Light Source at PSI. In the first set of experiments, we determined by use of XRR the distance between the surfaces and the electron density profile of the naturally present water across the hydrophilic gap at nominal zero humidity [3]. In the second set, the natural layer of K+ ions present on cleaved mica surfaces was substituted with monovalent Rb+ or divalent Sr2+ ions. In the third set droplets of RbCl, CsCl and BaCl2 solutions at different concentrations were nano-confined. We have quantitatively determined the minimum gap distance between the mica surfaces at ~ 105 Pa applied pressure under the influence of different surface ions and electrolytes. In all cases we have observed layered electron density profiles within the gap, with the layering generally being stronger for more strongly correlated systems. A comparison between confined chloride solutions with different monovalent and divalent cations (Cs+ , Rb+ and Ba2+) reveals cation specific effects which can be related to concentration, ion size and hydration behavior. For example, we observe characteristic differences between the relative proportions of hydrated inner- and outer-sphere species and in the coverages of the inner membrane surfaces by directly adsorbed ions. Moreover, ordering in strongly correlated BaCl2 is interpreted as alternate cation-anion layering. Structure models for the measured density profiles will be presented and discussed. References: 1. Israelachvili, J.N., Intermolecular and surface forces: revised third edition. 2011: Academic press. 2. Perret, E., et al., Molecular liquid under nanometre confinement: density profiles underlying oscillatory forces. Journal of Physics: Condensed Matter, 2010. 22(23): p. 235102. 3. Chodankar, S., et al., Density profile of water in nanoslit. EPL (Europhysics Letters), 2012. 99(2): p. 26001.
 Speaker: Dr. Saurabh Mani Tripathi Photonics Research Centre, Department of Computer Science and Engineering, University of Quebec at Outaouais, Canada. Title: Long period grating and multimodal interference effect based fiber-optic sensors Date: October 21st, 2013 Time: 3 pm - 4 pm Venue: FB 382 Abstract: In this seminar I will present my resent research activities on the development of fiber-optic sensors based on (I) long-period gratings and (ii) single-multi-single (SMS) fiber optic structures. The first part of my talk will deal with the development of bio-sensors for rapid, reliable and quantitative detection of pathogenic E. coli bacteria in water. In the second part I will discuss the role of a critical wavelength in the performance of fiber optic devices based on modal interference. Application of modal-interference effects in bio-therapy will also be discussed.

### Quic Talk:

 Speaker: A. Kani (Dept. Of Physics, IITK) Title: Harnessing quantum interference in atomic systems Date: October 7th, 2013 Time: 4 pm - 5 pm Venue: FB 382 Abstract: Quantum interference between the excitation pathways modifies the optical response of the atomic system and leads to Coherent Population Trapping (CPT) and/or Electromagnetic Induced Transparency (EIT), or Electromagnetic Induced Absorption (EIA), or Amplification without Inversion (AWI), or Enhanced Refractive Index with vanishing absorption. We will present a simple four-level atomic system interacting with a bi-chromatic light field (double V-system) and discuss all these quantum interference effects and discuss the way to control over these effects.

### Seminar:

 Speaker: Dr. Sayantani Bhattacharyya (Ramakrishna Mission Vivekanand University) Title: Detecting biomass burning emission over South East Asia from space. Date: September 16th, 2013 Time: 11 am - 12 am Venue: FB 382 Abstract: Fluid dynamics is controlled by Navier Stokes equation. On the other hand Einstein equations control the dynamics of classical gravity. Both are complicated non linear partial differential equations with rich structure in the space of solutions. As a consequence of AdS/CFT conjecture we expect a duality between the solutions to these two sets of equations at least in certain regime. The goal of this talk would be to explore this duality between these two very different systems.
 Speaker: Dr. Sourish Basu (SRON Netherlands Institute for Space Research, Utrecht, Netherlands) Title: Detecting biomass burning emission over South East Asia from space. Date: August 12th, 2013 Time: 04:00 pm - 05:00 pm. Venue: FB 382 Abstract: Among the different components constituting anthropogenic CO2 emissions, biomass burning is the most uncertain. Current methods to quantify emissions from biomass burning -- such as forest fires and agricultural waste burning -- include satellite imaging to detect burnt areas and smoke plumes. However, these methods often underestimate large fire events since satellite are blind in the presence of smoke and aerosols that accompany large fires. I will describe a different -- and still developing -- method to quantify biomass burning emissions, which is to derive surface fluxes of CO and CO2 from observed gradients of those gases. Since most areas with widespread fires are devoid of surface monitoring stations, the observed gradients will be derived from satellite data. I will show how, using independent measurements of CO and CO2, we can detect fire events and quantify the amount of biomass burned.
 Speaker: Dr. Pintu Das (Institute of Physics, Goethe University – Frankfurt, Germany) Title: Magnetization dynamics in nano-/micro-structures using 2DEG-based micro-Hall magnetometry Date: August 8th, 2013 Time: 04:00 pm - 05:00 pm. Venue: FB 382 Abstract: With the fast development of data storage technologies, studying the magnetization as well as domain-wall dynamics in magnetic nano- as well as micro-structures have recently found immense attention of researchers active in the field of magnetism [1]. Investigations have been carried out for arrays or assembly of magnetic particles of nanometer scale dimensions. However, measurements of assembly of particles lead to an average signal and during this process many interesting and important information get lost resulting in an incomplete understanding of the internal dynamics of individual domains or domain walls. Therefore, investigations of individual (i.e., single) magnetic entities of nano-/micron-scale dimensions are important in order to understand the magnetization process in great details. Such data can also be directly used to test the existing theories [2].Motivated by these factors, we performed magnetic measurements of single ferromagnetic particles of micron and nano-scale dimensions using micro-Hall magnetometry method based on two-dimensional-electron-gas (2DEG) in the heterostructure of GaAs/AlGaAs. In this talk, I will discuss the results of measurements on a single CrO2 micro-crystal. With our high-sensitive measurement method, we were able to observe the transition from three-domain state to a two-domain state with a single domain-wall (separating the two domains), which was supported by micro-magnetic simulations [3]. Furthermore, we were able to track the motion of the domain wall through the sample and observed Barkhausen jumps due to the interaction with the pinning centres. Overall, the results demonstrate that micro-Hall magnetometry measurements can be used to obtain quantitative and detailed information of magnetization reversal process in individual particles of nano and micron scale dimensions. The results also allow us to estimate the density of pinning centres as a function of temperature. References: [1] S. Parkin et al, Science, 320, 190 (2008). [2] K. S. Novoselov et al, Nature 426, 812 (2003). [3] P. Das et al., Appl. Phys. Lett. 97, 042507 (2010); J. App. Phys. 112, 053921 (2012).

### QuiC Talk:

 Speaker: Dr. Anand K. Jha (Dept. Of Physics, IIT Kanpur) Title: Temporal Coherence in Two-Photon Interference - II Date: July 4th, 2013 Time: 11:00 am - 12:00 noon. Venue: FB 482
 Speaker: Dr. Anand K. Jha (Dept. Of Physics, IIT Kanpur) Title: Temporal Coherence in Two-Photon Interference Date: June 18th, 2013 Time: 11:00 am - 12:00 noon. Venue: FB 482 Abstract: In the earlier two talks, we had discussed two-photon interference and entanglement from a very broad perspective. The aim of this talk (and the next few) is to get into in-depth discussions about two-photon interference and related phenomena. In this talk we will be discussing the role of temporal coherence and indistinguishability in two-photon interference. We will keep our discussions of temporal coherence centered around parametric down-conversion, a non-linear optical phenomenon that produces entangled two-photon field.
 Speaker: Dr. Kedar B. Khare (Dept. Of Physics, IIT Delhi) Title: How many measurements are needed to generate an N-pixel image? Date: June 10th, 2013 Time: 11:00 am - 12:00 noon. Venue: FB 382 Abstract: In Scientific and Technological research ranging from sub-nano to astronomical length scales, imaging systems are playing a key role as tools that allow us to visualize natural phenomena or objects of interest,thereby, directly influencing new discoveries. With ever increasing demands on imaging performance (e.g. resolution, speed, sensitivity to noise, etc.), it is becoming clear that imaging systems of tomorrow need to acquire, process and utilize imaging data in an efficient non-redundant manner. In this seminar I will discuss some current ideas on imagerecovery from "incomplete" or sub-Nyquist sampled data with examples from my own research work in diagnostic healthcare and optical imaging. It will be shown that a hybrid approach - combining imaging hardware and new image recovery algorithm ideas - allows us to overcome conventionally perceived limits on imaging systems.

### High Energy Physics Seminar:

 Speaker: Dr. Anurag Sahay ( Inst. of Physics, Bhubaneswar) Title: Tunnelling in Anti de Sitter Space and in its Boundary Matrix Dual Date: 07.06.2013 ( Friday) Time: 4:00 PM Venue: FB 382 Abstract: For charged black hole, within the grand canonical ensemble, the decay rate from thermal AdS to the black hole at a fixed high temperature increases with the chemical potential. We check that this feature is well captured by a phenomenological matrix model expected to describe its strongly coupled dual. This comparison is made by explicitly constructing the kink and bounce solutions around the de-confinement transition and evaluating the matrix model effective potential on the solutions.

### QuIC Talk (Quantum Information and Coherence)

 Speaker: Dr. Anand Kumar Jha (Dept. Of Physics, IIT Kanpur) Title: Two-Phonton Interference and Entanglement - II Date: May 7th, 2013 (Friday) Time: 4:15-5:15 pm Venue: FB-382

### QuIC

 Speaker: Dr. Anand Kumar Jha (Dept. Of Physics, IIT Kanpur) Title: Two-Phonton Interference and Entanglement - I Date: May 3rd, 2013 (Friday) Time: 3:45-5:00 pm Venue: FB-382

### Seminar:

 Speaker: Prof. S. Dutta Gupta (University of Hyderabad, Hyderabad) Title: Bending light the wrong way! Date: 17 April 2013 Time: 3.00 PM Venue: FB 382

### HEP:

 Speaker: Ravi Manohar (IITK) Title: A lightfront non-perturbative study of generalized parton distributions Date: March 12, Tuesday Time: 4 pm Venue: FB-382 Abstract: We give a study of interface between the nonperturbative lightfront amplitude calculation for an electron in a trap and an experimentally-accessible distribution functions using such light front amplitudes. It will be helpful to investigate these distribution functions at weak (QED) coupling as well as at an artificially large coupling. Additionally it will be interesting to map out the effects of a confining potential (external harmonic oscillator) trap on these distribution functions. Epoch to this project, we investigate the generalized parton distributions H(x,\zeta;,t) in the forward limit for a dressed-electron using the nonperturbative lightfront amplitude calculated in the harmonic oscillator basis.
 Speaker: Mridupawan Deka (JINR, Dubna, Russia). Title: Quark and Gluon Angular Momenta Contributions to Nucleon Spin Date: 26 February, Tuesday Time: 4 pm Venue: FB-382 Abstract: The nucleon spin structure has been a longstanding issue in hadronic physics, both experimentally and theoretically. From the polarized Deep Inelastic Scattering experiments and Lattice QCD calculations, it has been found that the contribution coming from the quark spin is rather small (~25%). Now, it is widely accepted that the rest of the nucleon spin should come from the gluon spin and the orbital angular momenta of quarks and gluons. In this talk, I will present a complete Lattice QCD calculation of the quark and glue angular momenta inside a proton. The calculation is carried out on a 16^3×24 quenched lattice using the standard Wilson action.

### Seminar:

 Speaker: Dr. R. Chelakkot, School of Engineering and Applied Sciences (SEAS), Harvard University, USA Title: Semiflexible polymers: Instabilities under confinement, constraint and activity. Date: 18 February (Monday) Time: 4:00 PM Venue: FB 382

### HEP:

 Speaker: Bindusar Sahoo (Nikhef, Amsterdam) Title: Topologically massive higher-spin gravity Date: February 13, wednesday Time: 4 pm Venue: FB-382 Abstract: In the last couple of decades a theory has been developed by Vasiliev to consider interacting theories of fields with spin greater than 2 which is known as higher-spin gravity. This theory has received a lot of attention recently in the context of AdS-CFT correspondence. The theory in various dimensions is conjectured to be dual to well known conformal field theories in the boundary. In the light of this recent development, we will discuss the higher-spin analogue of topologically massive gravity in three dimensions, which we call topologically massive higher-spin gravity. We will start with a brief introduction and motivation to consider higher-spin theories. This will be followed by a brief introduction and overview of current results in higher-spin theories and topologically massive gravity. This will be followed by our work on topologically massive higher-spin gravity. We will discuss various semi classical as well as quantum results of the theory considered by us.
 Speaker: Arnab Kundu (Univ of Texas at Austin) Title: Dynamics of Fundamental Flavours in Holographic Duals of Large N Gauge Theories. Date: Feb 4, 2013 Monday Time: 2:30 pm Venue: FB-382 Abstract: Using the gauge-gravity duality, more specifically the AdS/CFT correspondence, we will discuss strongly coupled dynamics of fundamental flavours in large N gauge theories. We will primarily focus on the physics of chiral symmetry breaking by introducing flavour degrees of freedom in the so called Klebanov-Witten model. We will discuss the physics of the flavour sector in and beyond the probe limit. We will conclude with some general remarks.

### Seminar:

 Speaker: Dr. Umakanta Tripathy (Visiting Scientist, TIFR, Mumbai) Title: Detecting malaria and imaging extra cellular matrix in tissues by multi-modal nonlinear laser scanning microscopy (NLSM) Date: 5th February, 2013 Time: 12:00 noon Venue: FB 382 Abstract: Multi-modal nonlinear laser scanning microscopy (NLSM), also known as multiphoton microscopy or higher harmonic generation microscopy is a powerful research tool that combines the advanced optical techniques of laser scanning microscopy with long wavelength multi- photon fluorescence excitation to capture high resolution and threedimensional (3D) images of specimens. Some of the core advantages that include label free imaging, depth imaging & minimizing photo-bleaching allows investigations on thick, living and fixed cells/tissues that would not otherwise be possible with conventional imaging techniques. Two-photon fluorescence (TPF), second harmonic generation (SHG), & third harmonic generation (THG) techniques are used as imaging tools. In the present talk, we will focus the use of multi-modal NLSM as an imaging device for the early detection and quantification of the malaria pigment (hemozoin) by THG technique. The obtained results will guide the optimal design of malaria detection technologies that exploit the THG response of hemozoin. In addition, multi-modal NLSM imaging of extra cellular matrix in tissues (collagen and elastin) to investigate the structural remodeling of the human ascending aorta with dilation, and documenting the geometrical properties of vocal folds (human & porcine) by SHG and TPF technique will also be presented. The results acquired would provide valuable information for better understanding the tissue biomechanics that may assist clinicians for rapid and reliable disease diagnosis.

### HEP:

 Speaker: Prof. Dharam Vir Ahluwalia (Universidade Estadual de Campinas, Brazil and TIFR) Title: Elko Spinors and dark matter Date: 17 January, Thursday Time: 11 AM - 1 PM and 4 PM - 6 PM (with refreshment breaks) Venue: 382 FB

### Seminar:

 Speaker: Dr. Prasanna Kulkarni, ( Departamento de Fisica de la MateriaCondensada,Universidad Autonoma de Madrid, Madrid,Spain ) Title: Elko Spinors and dark matter Date: 17 January, Thursday Time: 11 AM - 1 PM and 4 PM - 6 PM (with refreshment breaks) Venue: 382 FB
 Speaker: Title: Date: Time: Venue: Purnendu Chakraborty Gluon condensate and nonperturbative QCD propagators above deconfinement temperature 02 Jan 2013 (Wednesday) 4:00 PM (FB382) Speaker: Title: Date: Time: Venue: Udai Raj Singh Inhomogeneous superconducting gap and symmetry breaking in FeSe0.4Te0.6 studied by spectroscopic imaging STM 27 Dec 2012 (Thursday) 11:00 AM (FB382) Speaker: Title: Date: Time: Venue: Dr. T. Arun Kumar Study of perfluoropolymer as an alignment layer for nematic liquid crystals 27 Dec 2012 (Thursday) 4:00 PM FB382 Speaker: Title: Date: Time: Venue: Prof. Dharam Vir Ahluwalia Elko Dark Matter 24 Dec 2012 (Monday) 4:00 PM FB382 Speaker: Title: Date: Time: Venue: Dr. Amar Nath Gupta Transition path time, diffusion constant and folding rate of protein determined from reconstructed free-energy landscape analysis 12 Dec 2012 (Wednesday) 4:00 PM (FB382) Speaker: Title: Date: Time: Venue: Dr. Shiva Kumar Malapaka, Leeds University, UK A study of magnetic helicity in forced and decaying 3D-MHD turbulence 4 pm FB-382 Speaker: Title: Date: Time: Venue: Dr. Anindya Das Superconductor-semiconductor junctions: Cooper pairs splitting and Majorana quasiparticles 22 Nov 2012 (Thursday) 4:00 PM (FB382) Speaker: Title: Date: Time: Venue: Dr. Naveen Kumar Relativistic beam-plasma interaction and its applications for particle acceleration and fast ignition fusion in plasmaa 20 Nov 2012 (Tuesday) 11:00 am FB 382 Speaker: Title: Date: Time: Venue: T. K. Saxena Automation in research and industry 6th Nov 2012 (Tuesday) 4:00 pm FB 382

 Speaker: Title: Date: Time: Venue: Dr. Dinesh Kabra, Cavendish Laboratory, University of Cambridge, UK. Molecular Semiconductors: Charge Transport, Structural and Spectroscopic based Investigations 12 Jan 2012 (Thursday) 4:00 pm FB 382 Speaker: Title: Date: Time: Venue: Swarn Lata Singh (BHU)) Free-energy functional for symmetry broken ﬁrst order phase transitions 11 January 2012 4:00 pm FB 382 Speaker: Title: Date: Time: Venue: Dr. Amit Agarwal (Scoula Normale, Pisa, Italy) Collective excitations in strongly spin-orbit coupled two dimensional electron gases 2 January 2012 4:00 pm FB 382 Speaker: Title: Date: Time: Venue: Pomita Ghoshal (HRI) Determining the Neutrino Mass Hierarchy via Future Atmospheric Neutrino Detectors December 30 (Friday) 4:00 pm FB 382 Speaker: Title: Date: Time: Venue: Dr. Chary Rangayajulu, University of Saskatchewan, Canada Laser Compton Scatter MeV Photons at Light Sources for Nuclear andAllied Sciences 19th December, 2011 (Monday) 4:00 pm FB 382 Speaker: Title: Date: Time: Venue: Dr. Amit Sharma, Seagate Technology, USA An Integrated Heat Assisted Magnetic Recording System 2nd November, 2011 (Wednesday) 2.30 pm FB 382 Speaker: Title: Date: Time: Venue: Gopal, IITK Collider Implication of Weyl Meson. 18 October, Tuesday 4.00 pm FB 382 Speaker: Title: Date: Time: Venue: M. Ranaul Islam (Strathclyde University, Glasgow, UK) Laser Wakefield Accelerator: Towards Gamma-Rays 17 October, 2011 4.00 pm FB 382 Speaker: Title: Date: Time: Venue: Dr. Anand Kumar Jha, Intel Corporation, USA Two-Photon Fields: Coherence, Interference and Entanglement 27 September, 2011 (Tuesday) 4.00 pm FB 382 Speaker: Title: Date: Time: Venue: Kaushik Bhattacharya (IITK) Lee-Wick thermodynamics and its effect in the early universe 20 Sept, 2011, Tuesday 4.00 pm FB 382 Speaker: Title: Date: Time: Venue: Dr. Soumen Mandal, Institut Neel, CNRS and Universite Joseph Fourier,BP 166, 38042 Grenoble cedex 09, France Diamond as a material for nano-mechanical and quantum devices 7 Sept, Wednesday 4.00 pm FB 382 Speaker: Title: Date: Time: Venue: Dr. Archana Tiwari, School of Chemical and Physical Sciences, Sikkim University Fluorescent balls with an effective spin 06 Sept 2011 (Tuesday) 2.30 pm FB 382 Speaker: Title: Date: Time: Venue: Prabhakar Tiwari (IITK) Large Scale Alignments in Quasar Polarizations due to pseudoscalar-photon mixing in intergalactic magnetic fields Sept 06, Tuesday 4.00 pm FB 382 Speaker: Title: Date: Time: Venue: Dr. Swati Bhattacharya (Univ. of Illinois, Urbana, USA) Designing nanopore sensors: laying the foundations of personalgenomics 5 September, 2011 4.00 pm FB 382 Speaker: Title: Date: Time: Venue: Dipankar Chakrabarti (IIT Kanpur) A study of generalized parton distributions in position space. 23 Aug, Tuesday 4.00 pm FB 382 Speaker: Title: Date: Time: Venue: Udit Raha (Univ. Basel) Electromagnetic Pion and Kaon Form Factors in Light-cone QCD 17 Aug, Wednessday 5.00 pm FB 382 Speaker: Title: Date: Time: Venue: Kumar Rao (Helsinki Univ) Top Polarization as a probe of New Physics 02 Aug(Tuesday), 2011 4.00 pm FB 382 Speaker: Title: Date: Time: Venue: Dr. Amitesh Paul, Technische Universität München, Germany Polarized neutron scattering in nano-layered systems 01 August 2011 (Monday) 4.00 pm to 5.00 pm FB 382