04-09-2017 At 03:00:00 PM
Speaker: Prof. R. Rajaraman, Emeritus Professor of Physics, Jawaharlal Nehru University, New Delhi
Category: Colloquium
Venue: IOP Lecture Hall
Pulsars (nickname for Pulsating Sources of Radio) were discovered in 1967 by Jocelyn Bell and Anthony Hewish. They are remarkable objects in the sky from which blips (pulses) of radio waves are detected by radio telescopes. The pulses are so regular in frequency that it was wonderedin the immediate aftermath of their discovery whether they were the much awaited signals from an alien civilization! But through a combination of observation and theory, it was soon realised that a Pulsar is in fact one giant rotating nucleus.
After a brief introduction to Pulsars and their formation, the talk will focus on what is likely to be their internal composition and why they are also called "Neutron Stars".
The talk will be very introductory, meant for students from all branches of Physics. But near the end we will briefly discuss some very fundamental concepts of elementarily, that play a role in the equation of state of the pulsars.
08-09-2017 At 04:00:00 PM
Speaker: Er. Sanjib Kumar Sahu, IOP, Bhubaneswar
Category: General Interactive Session
Venue: IOP Lecture Hall
LabView and its interface to experimental instruments
19-09-2017 At 04:00:00 PM
Speaker: Dr. Helder Marchetto, Germany
Category: Seminar of General Interest
Venue: IOP Lecture Hall
EMSI - IOP Lecture Series on Microscopy
20-09-2017 At 11:45:00 AM
Speaker: Dr. B.K.Sahoo, SO/F, Radiological Physics and Advisory Division of BARC, Mumbai
Category: Seminar of General Interest
Venue: IOP Lecture Hall
Presentation on the Earthquake Precursor Monitoring Station established at IOP
13-10-2017 At 04:00:00 PM
Speaker: Dr. Saurabh Niyogi, Gokhel Memorial College, Kolkata
Category: HEP Seminar
Venue: IOP Lecture Hall
A compressed spectrum pose a serious challenge at LHC. Such a spectrum naturally arises in various BSM scenarios. Monojet with missing pT has been the conventional signal at the LHC. However, we stress that inclusion of $p_T$-binned track observable from such soft objects provide very efficient discrimination of new physics signals against various SM backgrounds. We perform a detailed cut-based and multivariate analysis (MVA) for two benchmark points in MUED and pMSSM scenarios to show that the parameter space of those models can be probed in the ongoing run of LHC at 13 TeV center-of-mass energy with an integrated luminosity 20-50 fb^{-1}.
16-10-2017 At 04:00:00 PM
Speaker: Arnab Roy, Department of Physics, Bar-Ilan University, Ramat-Gan, Israel
Category: CMP Seminar
Venue: IOP Lecture Hall
The superconductor-insulator transition (SIT) is an excellent example of a quantum phase transition, controlled by a non-thermal tuning parameter g, and dominated by quantum fluctuations, which are expected to be prominent near the quantum critical point. So far, most of the experimental studies of the SIT have focussed on transport properties and tunnelling studies, which do not provide quantitative information on the criticality, and on the physics of the quantum fluctuations close to the transition. In our study, we utilize an experimental tool uniquely suited for the study of the evolution of quantum fluctuations through the quantum critical point: the Nernst effect. Nernst effect, in the past has proved to be a very useful tool in the study of superconducting fluctuations, particularly in the case of phase fluctuations mediated by mobile vortices and antivortices. Such fluctuations are important below the superconducting critical temperature TC, and are responsible for having a finite resistance even at a temperature below TC, at which a finite superconducting amplitude ψ¬0 appears.
In our system of amorphous thin film of Indium Oxide, it is believed that the attainment of zero resistance is mediated by pairing of the mobile vortices and antivortices into immobile dipoles, at a temperature TBKT below TC, the transition being a Berezinskii-Kosterlitz-Thouless (BKT) transition. Using resistivity as our tuning parameter g, we take this system through a disorder-induced SIT, and find significant Nernst signals on both the superconducting and insulating sides of the SIT. Analysis of the Nernst coefficient across the SIT shows remarkable qualitative agreement with a model recently developed for the case of Josephson-coupled superconducting chains [1]. We also obtain, for the first time, the scaling behaviour of the off-diagonal Peltier coefficient αyx, a thermodynamic quantity closely related to the Nernst effect, near a disorder-induced SIT.
References:[1] Y. Atzmon and E. Shimshoni, Phys. Rev. B - Condens. Matter Mater. Phys. 87, 1 (2013).
16-10-2017 At 12:00:00 PM
Speaker: Mr. Nirakar Sahoo, IIT Hyderabad
Category: HEP Seminar
Venue: IOP Lecture Hall
The Dark Matter constitutes nearly 26.8% of the total energy budget of the universe as precisely measured by PLANCK and WMAP. One of the attractive candidates for dark matter is a Weakly Interacting Massive Particle(WIMP). A minimal model is proposed which contains one triplet scalar with hypercharge 2 and two vector like fermions: one singlet and a doublet in order to simultaneously explain neutrino mass and dark matter content of the universe.
The dark matter emerges out as a mixed state of the singlet fermion and the neutral component of the doublet. A Z2 symmetry stabilizes the dark matter. The triplet scalar gets an induced vev after the electroweak symmetry breaking and hence give Majorana masses to the neutrinos as well as to the dark matter. Due to the Majorana mass term of the dark matter, the Z mediated direct detection cross-section is forbidden but it can interact with the nuclithrough Higgs mediated chanel and hence can be probed in future running experiments like Xenon-1T. The charged companion of dark matter can give large displaced signature at the LHC.
17-10-2017 At 04:00:00 PM
Speaker: C. Soumya, University of Hyderabad
Category: TPSC HEP Seminar
Venue: IOP Lecture Hall
The discovery of neutrino oscillation made a major breakthrough in particle physics as it implies that neutrinos have mass and thus provides very strong evidence for new physics beyond the SM. So far huge progress has been made in extracting the information about the knowledge of the neutrino masses and lepton flavour mixing parameters through the various neutrino experiments. However, there is no information about the mass hierarchy of neutrino, CP violation in neutrino flavor transition and octant of atmospheric mixing angle.
All these parameters play crucial role in neutrino mass model building. Therefore, many neutrino oscillation experiments are intended to determine these unknowns. This talk presents a sensitivity of current (T2K and NOvA) and future (T2HK) generation experiments to determine the unknowns in this sector.
This is followed by a discussion on how do non-standard interactions of neutrino affect the sensitivity of LBL experiments. Finally, this talk also presents a study on the non-unitary lepton mixing in an inverse seesaw and its impact on the sensitivity of LBL experiments.
17-10-2017 At 11:00:00 AM
Speaker: Mr. Arpan Das
Category: Synopsis presentation
Venue: IOP Lecture Hall
Synopsis presentation
25-10-2017 At 04:00:00 PM
Speaker: Prof. P.K Mohanty, SINP, Kolkata
Category: Colloquium
Venue: IOP Lecture Hall
02-11-2017 At 04:30:00 PM
Speaker: Dr. Sangram Das
Category: Review talk
Venue: IOP Lecture Hall
Review talk
03-11-2017 At 04:00:00 PM
Speaker: Sabya Sachi Chatterjee
Category: HEP Seminar
Venue: IOP Lecture Hall
Synopsis presentation
08-11-2017 At 04:00:00 PM
Speaker: Tapoja Jha, University Of Calcutta
Category: HEP Seminar
Venue: IOP Lecture Hall
In this talk, we will discuss Universal Extra Dimensional models (UED) in its basic and non-minimal version (nmUED). Non-minimality in Universal Extra Dimensional (UED) framework is realized by adding boundary localized terms (BLT). We will discuss the unitarity constraints in gauge and scalar sectors. We shall show that some of the tree-level two-body scattering amplitudes in gauge and scalar sectors do not respect partial wave unitarity. Unitarity of scalar sector of this model leads to an upper bound on gauge or scalar BLT parameter which depends on the maximum number of Kaluza-Klein (KK) mode considered in the analysis. We shall also show the limit on compactification radius of UED in view of the Zbb coupling. For suitable choice of BLT parameters (which is permissible from unitarity analysis), 95% C.L. lower limit on inverse of compactification radius comes out to be in the range of 1 TeV in the framework of nmUED. Finally, we will discuss some flavor changing top quark decays. In UED these decay rates do not change much from their Standard Model (SM) values. However, in nmUED these decay rates can be higher than SM for specific choices of the BLT parameters for a certain range of inverse compactification radius. But these model parameters may lead to Kaluza-Klein particle masses that are in tension with the LHC and LEP bounds.
13-11-2017 At 04:00:00 PM
Speaker: Professor Sreerup Raychaudhuri, TIFR, Mumbai
Category: Colloquium
Venue: IOP Lecture Hall
IOP Colloquium series in memory of Prof. Durga Prasad Roy
14-11-2017 At 04:00:00 PM
Speaker: Sudipta Mahana
Category: Synopsis Talk
Venue: IOP Lecture Hall
Synopsis Talk
14-11-2017 At 11:00:00 AM
Speaker: Dr. Alestin Mawrie, Dept. of Physics, IIT Kanpur
Category: CMT Seminar
Venue: IOP Lecture Hall
8-Pmmn borophene is a polymorph of borophene that exhibits anisotropic tilted Dirac cones. In our work, we have done a detailed theoretical study of the optical conductivity of 8-Pmmn borophene. We provide exact analytical expressions of the maximum optical conductivity. We also obtain exact analytical expressions of the minimum energy (1) required to trigger the inter-band optical transitions and energy (2) needed to attain maximum optical conductivity. We find that the optical conductivity are highly anisotropic as a consequence of the anisotropic Dirac cone. The optical conductivities have a non-monotonic behavior with photon energy in the regime between 1 and 2, as a result of the tilted parameter . The tilted parameter can be extracted by knowing 1 and 2 from optical measurements.
The maximum values of the components of the optical conductivity do notdepend on the carrier density and the tilted parameter. The product of the maximum values of the anisotropic conductivities has the universal value (e2=4h2 ). The tilted anisotropic Dirac cones in 8-Pmmn borophene can be realized by the optical conductivity measurement.
Reference: S.Verma, A. Mawrie and T. K. Ghosh, Physical Review B 96, 155418 (2017).
15-11-2017 At 03:30:00 PM
Speaker: Professor Gobinda Majumder, TIFR, Mumbai
Category: Colloquium
Venue: IOP Lecture Hall
IOP Colloquium series in memory of Prof. Durga Prasad Roy
20-11-2017 At 04:00:00 PM
Speaker: Dr. Poonam Mehta, JNU, New Delhi
Category: TPSC HEP Seminar
Venue: IOP Lecture Hall
The study of CP violation addresses fundamental questions such as - are the laws of physics the same for matter and anti-matter. CP is a discrete symmetry of nature given by a product of two quantities : charge conjugation (C) and parity (P). Detecting leptonic CP violation is one of the most challenging goals in particle physics today. An attractive possibility to measure CP phase is via long baseline accelerator experiments such as Deep Underground Neutrino Experiment (DUNE). In this talk, we will show that clean extraction of CP violating phase becomes a formidable task in presence of new physics. We discuss one possible experimental strategy to distinguish between standard paradigm and the new physics scenarios.
22-11-2017 At 04:00:00 PM
Speaker: Professor Amol Dighe, TIFR, Mumbai
Category: Colloquium
Venue: IOP Lecture Hall
IOP Colloquium series in memory of Prof. Durga Prasad Roy
24-11-2017 At 03:00:00 PM
Speaker: Professor Rohini M. Goldbole, CHEP, IISc, Bangalore
Category: Colloquium
Venue: IOP Lecture Hall
IOP Colloquium series in memory of Prof. Durga Prasad Roy
28-11-2017 At 11:00:00 AM
Speaker: Bidisha Chakraborty
Category: Ph.D. Defense Seminar
Venue: IOP Block-B Lecture Hall
Extremal Black hole microstate geometries have been well studied in the context of the black hole information puzzle and the fuzzball proposal. Non-extremal black hole microstates are much more interesting but less explored. Using the AdS/CFT prescription, we identify a general class of dual states of non-supersymmetric orbifolded D1-D5-P supergravity solutions (JMaRT). We compute the massless scalar emission spectrum and emission rate both in the gravity and CFT sides and show that they match perfectly, thus providing strong evidence for our identification. We also study pair creation like picture from the ergoregion of these geometries. We further present novel approaches to construct these solutions systematically using group theory techniques. Higher dimensional gravity theories when dimensionally reduced to two dimensions manifest infinite number of symmetries. The infinite dimensional symmetry group is known as the Geroch group. We construct Geroch group SL(3,R) matrices for the 5D Myers-Perry and Kaluza-Klein black holes. Moreover we construct the non-BPS D1-D5-P JMaRT solution using inverse scattering method followed by group theory techniques. We show that these solutions can be thought of as charged Euclidean 5D Myers-Perry instanton.
29-11-2017 At 04:00:00 PM
Speaker: Professor Rajiv V. Gavai, TIFR, Mumbai
Category: Colloquium
Venue: IOP Lecture Hall
IOP Colloquium series in memory of Prof. Durga Prasad Roy
01-12-2017 At 04:00:00 PM
Speaker: Prof. M. P. Das, Department of Theoretical Physics, The Australian National University
Category: Colloquium
Venue: IOP Lecture Hall
Einstein had an enigmatic ability to arrive at powerful conclusions using a few well-known assumptions. Explanation of the Photoelectric effect is a bright example of that. In this talk we retrospect the so-called quantum revolution beginning with the photoelectric phenomenon. Following this historical endeavor, we present post-Einstein development of theories and experiments on photoemission from solids.
05-12-2017 At 10:30:00 AM
Speaker: Prof. M. P. Das, Department of Theoretical Physics, The Australian National University
Category: Lecture Series
Venue: IOP Lecture Hall
Lecture series on QUANTUM TRANSPORT IN MESOSCOPIC SYSTEMS
06-12-2017 At 04:00:00 PM
Speaker: Prof. Sumathi Rao, HRI, Allahabad
Category: Colloquium
Venue: IOP Lecture Hall
Along with a brief introduction to the phenomenon of the integer quantum Hall effect, I will briefly review edge reconstruction due to Coulomb interactions and changes in the smoothness of the edge potential. Then I will describe some recent work where we show how exchange interactions can cause a switching of the spin of the edge modes, causing like spins to come close to each other.
07-12-2017 At 10:00:00 AM
Speaker: Prof. M. P. Das, Department of Theoretical Physics, The Australian National University
Category: Lecture Series
Venue: TBD
Lecture series on QUANTUM TRANSPORT IN MESOSCOPIC SYSTEMS
11-12-2017 At 10:00:00 AM
Speaker: Prof. M. P. Das, Department of Theoretical Physics, The Australian National University
Category: Lecture Series
Venue: TBD
Lecture series on QUANTUM TRANSPORT IN MESOSCOPIC SYSTEMS
12-12-2017 At 04:00:00 PM
Speaker: Puspendu Guha
Category: Synopsis Talk
Venue: IOP Lecture Hall
Thesis Supervisor: Prof.P.V.Satyam
Committee Members: Prof.A.M. Jayannavar(chairman), Prof. Shikha Varma, Prof.S.K Patra
15-12-2017 At 04:00:00 PM
Speaker: Dr. P.K. Muduli, IIT Delhi
Category: CMP Seminar
Venue: IOP Lecture Hall
Spin Hall Effect (SHE) and its inverse enables generation, manipulation and detection of pure spin current [1,2] in heavy metal thin films. The most common heavy metal that is heavily investigated is Pt. The β-phase of Ta and W offer higher spin Hall angle [3, 4] compared to Pt. However, there is significant variation in the values of spin Hall angle reported in the literature for both Ta and W. In this work, we explore the electrical and optical detection of spin currents of sputtered Ta thin films using Spin torque ferromagnetic resonance (STFMR), inverse spin Hall effect (ISHE) and magneto-optical Kerr (MOKE) measurements. In STFMR measurement, we show an anti-damping spin-orbit torque in epitaxial-Py/β-Ta that leads to nearly 30 % modulation of the effective Gilbert damping constant. The observed torque cannot be explained using the spin Hall effect and may arise from the interface or the crystalline structure of Py thin films [5]. We demonstrate a strong correlation of measured ISHE voltage with crystalline phase of Ta thin films and found a large spin Hall angle for a mixed crystalline phase of Ta.
We optically detect spin accumulation due to the spin Hall effect in single layer Ta films by applying a square wave current and using Fourier analysis in a MOKE setup that uses spatially modulated incident light. We show that there exists a threshold current density (Jth) above which spin current can be detected via the optical technique. Jth, which is a measure of spin current efficiency, is found to be the lowest in the mixed phase of Ta and is strongly correlated with the crystalline phase of Ta [6].
References
[1] J. E. Hirsch, Phys. Rev. Lett. 83, 1834 (1999);
[2] S. O. Valenzuela and M. Tinkham, Nature 442, 176-179 (2006).
[3] Liu, L.Q. et al., Science 336,555-558(2012).
[4] Pai, C.F. et al., Appl. Phys. Lett. 101, 122404(2012).
18-12-2017 At 04:00:00 PM
Speaker: Dr. Swagata Mukherjee, RWTH Aachen University, Germany
Category: HEP Seminar
Venue: IOP Lecture Hall
The latest results of searches for exotic new physics from the CMS collaboration will be presented. The primary focus will be the searches of new particles decaying to leptons, including hadronically decaying tau leptons. Experimental signatures involving leptons are one of the cleanest probes of new physics at the LHC. These searches are based on proton-proton collision data at the LHC. In this talk, the status of data scouting will also be presented. CMS collaboration introduced the concept of data scouting as an alternative strategy to normal data-taking technique, allowing to take data that otherwise would be rejected by the trigger filters. This special data flow, based on event-size reduction rather than event filtering, is considered as a coherent discovery tool, and will be reviewed in this talk.
19-12-2017 At 04:00:00 PM
Speaker: Dr. Alain Claverie, CEMES-CNRS and University of Toulouse, France
Category: Colloquium
Venue: IOP Lecture Hall
Today, the Smart Cut TM technology is currently used to transfer sub-micrometer thick layers of many crystalline materials (Si, Ge, SiGe, GaN, SiC, Ferroelectrics) onto various substrates. This technology is based on the ion implantation of hydrogen and/or helium in the material to be transferred and on the bonding of this material onto another material, followed by thermal annealing.In this talk, we will review the knowledge we have recently gained of the different mechanisms by which the implanted H/He evolve during annealing finally leading to the fracture and separation of the surface layer.We will identify the different defects which play a role in this phenomenon (VnHm complexes, platelets, micro-cracks) and of the mechanisms by which they grow and eventually transform from one into the other. This discussion will be based on large collection of TEM, Raman, FTIR and X-rays data, including direct imaging of some of these transformations in situ, in the microscope. Finally, we will identify and discriminate the mechanisms driving "gentle" transformations dictated by thermodynamics (nucleation, diffusion, Ostwald ripening) from those driving "catastrophic" transformations (strain assisted coalescence, fracture propagation). Remaining questions to be answered before the full simulation of the process is thinkable will be indicated. The possible extension of this technology to the direct transfer of ultra-thin layers (<50 nm) will be discussed.
27-12-2017 At 03:00:00 PM
Speaker: Dr. Mrutyunjaya Bhunya
Category: Seminar of General Interest
Venue: IOP Lecture Hall
Seminar of General Interest