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PROGRAMME

DAY 1 : 22nd April, 2022 (Friday) Afternoon | VENUE : Central Lecture Theatre (CLT)

2.30 pm Inauguration by   Prof. Arul Lakshminarayan

2.30 pm to 3 pm Introductory Remarks by Prof. V. Balakrishnan

3.00 PM TO 3.30 PM           TEA

  Time

Speaker

Title of the Talk

LINK
SESSION 1 | CHAIR : Prof. C. Vijayan

15:30

Prof Prem B Bisht Nano-micro whispers and ultrafast optical phenomena
ABSTRACT This talk will give a overview of the activities in this area in last few years in our research group.

16:00

Prof. Sunethra Ramanan Low-momentum interactions for ultracold Fermi gases
ABSTRACT The main focus of the talk is to study a system of ultracold Fermi gas from the BCS to the unitary regime, using low-momentum effective interaction that preserve experimental observables such as scattering length and pairing gaps up to the Fermi momentum. The goal will be to calculate the equation of state using many-body perturbation theory as well as Bogoliubov many-body perturbation theory. In particular I will discuss the Bertch parameter in the unitary regime and its dependence on the renormalization scale.

16:30

Prof. Shantanu Mukherjee Proximity induced superconductivity in Quantum Spin Hall Insulator, Monolayer 1T’-WTe2
ABSTRACT 2D Quantum Spin Hall Insulators (QSHI) have an insulating surface and a helical conducting edge state, that is topologically protected against disorder effects. The conducting edge state can host non trivial edge states in the presence of an external magnetic field and an induced superconducting gap. Here, I will discuss a short story of a monolayer of dichalcogenide material 1T’-Wte2 when placed over an s-wave superconductor NbSe2.

17:00

Tulika Agrawal Cavity quantum electrodynamics in fluorescent nanodiamonds coupled cavity system​
ABSTRACT Optical cavities lead to whispering gallery modes (WGMs) having high quality factors and low volumes. The applications of WGMs include micro-lasing, nonlinear optics, Raman spectroscopy, optical waveguides and cavity quantum electrodynamics (CQED). The coupling between an emitting atom and the cavity modes are described by CQED. In the weak coupling regime, the radiative rate of the emitter gets modified and is known as Purcell effect. One of the promising candidate for the photostable and intense emitter is fluorescent nanodiamond (ND). Nitrogen vacancy (NV) embedded NDs have spin triplet ground and excited states which makes them beneficial in quantum computing and cryptography. ND coupled cavity has exhibited the modification in lifetime of ND which is further used to determine its homogeneous linewidth.

17:15

Mayank Gupta Spin texture as a polarization fingerprint of halide perovskites
ABSTRACT Hybrid organic-inorganic halide perovskites (HOIP) are discovered to be a promising class of materials for optoelectronics, and spinorbitronics due to the presence of strong spin-orbit coupling and spontaneous ferroelectric polarization. Due to strong sp-hybridization derived antibonding states at the band edges, they provide a near-ideal platform to study a few excellent quantum coupling effects. Furthermore, these interactions can also be tuned easily by breaking symmetries, doping, and applying external strain. Here, we develop a model Hamiltonian to describe such interactions using the electronic structure and spin texture analysis in HOIP. The Hamiltonian takes into account the electron hopping, spin-orbit coupling, and the effect of the polarized field. We apply the strain and uniform pressure in these halide perovskites to study the various topological features emerging through the band inversion near the Fermi level. Further, we infer that the spin texture is far more sensitive to the polarized field and can be served as a fingerprint for the HOIPs. The formation of cusp and nodes in the spin texture spanned across the Brillouin zones well as possible hybridization in the spin texture, driven through band inversion, can give rise to a unique spin transport phenomena in these perovskites. Furthermore, we will see the polarized field can lead to first order normal to topological phase transition and can create unconventional topological phases in the form of Dirac circles and arches. We support our findings with density functional calculations.

17:30

Subhamoy Sahoo Identifying type of excitons in organic semiconductors using electric field modulation spectroscopy
ABSTRACT Excitons play a key role in determining the optical and electrical properties of organic semiconductors. Upon excitation, primarily Frenkel and charge-transfer excitons are formed in these systems. Frenkel excitons are preferable in organic light-emitting devices due to their high recombination probability. In contrast, the dissociation probability of the charge transfer excitons is high due to its comparatively low binding energy, which is suitable for organic photovoltaic devices. Therefore, it is essential to identify the type of excitons generated in the system, to understand its optoelectrical properties. In this work, we use electric field modulation spectroscopy, a non-destructive technique, to probe the nature of excitons in organic semiconductors and their heterostructures. In the presence of an electric field, the absorption and emission properties of the organic semiconductors change. Here, we primarily discuss the change in absorption of the system in the presence of field and the effect of optical interference in the measurements.

17:45

Rabindev Bishal A recurrence study of the vocal development of a juvenile canary song
ABSTRACT The early vocal development of a canary has significant consequences on its bird song. These effects are characterized via a recurrence study. The songs of a canary bird are recorded at different stages in the early development part of its vocal system. The syllabic sequences from each recorded song are extracted and quantified by a features vector, a finite element representation of spectral and temporal properties. The recurrence plot of these vectors of the syllabic sequences shows a characteristic self-similar pattern that gets more organized and shows the gradual development of recurrent structures in the syllabic sequences with the increase in vocal development. Quantities such as laminarity (defined from the recurrent vertical lines in the recurrence plot) and determinism (defined from the recurrent diagonal lines in the recurrence plot) show an increase in the vocal development of the bird with increasing age. Thus, the recurrence plots and the associated computed quantities demonstrate the increasing control on the syllabic sequences, which emerges with the increase in vocal development at different stages.

DAY 2 : 23RD April, 2022 (Saturday) | VENUE : Central Lecture Theatre (CLT)

SESSION 2 | CHAIR : Prof. M. S. Ramachandra Rao

09:00

Prof Markandeyulu Magnetic properties of Mn-M (M=Mn, Fe, Co)-Sb intermetallics
ABSTRACT The intermetallic MnSb crystallizes in the hexagonal NiAs-type structure in which, Mn atoms and Sb atoms occupy 2a (0, 0, 0) sites and 2c (1/3, 2/3, 1/4) sites, respectively. In addition, two vacant 2d (2/3, 1/3, 1/4) sites are available in the structure. The magnetic properties of Fe, Co added MnSb will be discussed. MnFe0.25Sb exhibits an antiferromagnetic-AFM (ferromagnetic-FM) like behaviour at low (high) temperatures. Mn moments at the 2a site are antiparallel (possibly a canted AFM) to each other along the c-direction whereas, Fe moments at the 2d site are neither parallel nor antiparallel to the Mn moments at the 2a site. Mn (Mn1) at the 2a site carries a magnetic moment of 4.24 (-4.15) µB and Fe carries a magnetic moment of -2.38 µB. Furthermore, Sb too carries a small magnetic moment of -0.02 µB. Mn – Mn exchange as well as that between Mn and Fe moments are antiferromagnetic; the competition between these two interactions may lead to a non-collinear antiferromagnetic like state in the ground state. MnCo0.25Sb exhibits two transitions at 152 K and 292 K. The transition at 292 K is a ferromagnetic to paramagnetic transition and the transition at 152 K is spin re-orientation transition of Co moments, in which the Co moments at the 2d site gradually align antiparallel with respect to the Mn moments at the 2a site as temperature decreases.

09:30

Prof. Rajesh Singh Flow-induced bound states of active particles
ABSTRACT Active particles - such as microorganisms - create fluid flow around them, even when stationary, due to nonequilibrium processes on their surfaces. This flow leads to the interaction of an active particle with other particles and boundaries in the bulk fluid. In this talk, I will present a theory to compute such fluid-mediated interactions in active particle suspensions by obtaining an expression for hydrodynamic forces and torques. The explicit forms of these forces and torques allow the determination of mechanisms for forming bound states of active particles in distinct experimental settings. I will use these results to rationalize recent experiments in active matter.

10:00

Akash Mohapatra Thermal transport in graphene: role of rotational stacking disorder and local curvature
ABSTRACT We examined thermal transport across wrinkles in CVD-grown few-layer graphene samples using Raman optothermal technique supported with finite-element simulations. The thermal conductivity of unwrinkled regions was measured as, k ~ 165 W/mK. Measurement at the wrinkle sites revealed local enhancement of thermal conductivity, with k ~ 225 W/mK. Furthermore, the total interface conductance of wrinkled regions decreased by more than an order in magnitude. The physical origin of these observations is discussed. We also discuss the effect of rotational stacking faults and turbostraticity on the thermal conductivity of multilayer graphene.
10:15 Merin Jose Self-assembly of soft colloids
ABSTRACT Colloidal self-assembly is a smart technique widely exploited to fabricate complex materials from the bottom-up and useful for numerous applications. Colloidal crystals formed through self-assembly route show long-range ordering and also mimics physical properties displayed in their atomic counterparts. Our interest lies on a special class of colloids, namely, soft colloids, that show intermediate behaviour between polymers and hard spheres. We study the evaporative self-assembly of soft colloids composed of poly (N-isopropyl acrylamide) (p-NIPAM) microgels. In this talk, I will give an overview of the properties of the microgels that we have exploited to modulate the self-assembly in monolayer particulate deposits and the evaporation kinetics of droplets loaded with microgels.
10:30 Anita Lavania Amplitude analysis of the decay $D^0 \to K_{\rm L}^0\pi^+\pi^-$ at BESIII
ABSTRACT We present a study performed to model the resonant amplitude structures of the decay mode $D^0 \to K_{\rm L}^0\pi^+\pi^-$, using the quantum-correlated $D^0\bar{D}^0$ data produced at $\sqrt{s}=3.773$ GeV at BESIII, corresponding to an integrated luminosity of $2.93$ fb$^{-1}$. This is the first amplitude analysis study of a decay mode involving a $K_{\rm L}^0$ that reports the first data driven measurement of the complex {\it U-spin breaking parameters} ($\hat{\rho}$) related to various $CP$-eigenstate resonant modes. The radial components of the $\hat{\rho}$ parameters in this study are observed to take central values in a wide range from $0.37$ to $12.21$ in contrast to the assumed value of unity in the previous analyses. Other fit results in the form of fractional resonant contributions and strong-phase parameters $c_i^{(')}$ and $s_i^{(')}$ for both $K_{\rm S}^0\pi^+\pi^-$ and $K_{\rm L}^0\pi^+\pi^-$ modes, comparing them with the model-independent BESIII results are also included.

10:45

Pritam Kalbhor Angular analysis of the rare decay Bs → φµµ
ABSTRACT New Physics (NP) beyond the Standard Model (SM) can be uncovered by analyzing processes that are expected to occur with very low probability in the SM. Angular analysis of rare decay Bs ? fµµ is studied, using proton-proton collision data collected by CMS experiment at center-of-mass energies of 13 TeV. Observables describing angular distributions of Bs ? fµµ decay are determined in different regions q^2, the square of the dimuon invariant mass

11:00-11:30                       TEA

SESSION 3 | CHAIR : Prof. Jim Libby

11:30

Prof Sriramkumar Observational probes of non-trivial inflationary and post-inflationary dynamics over small scales.
ABSTRACT The primordial scalar power spectrum is well constrained over large scales, essentially by the observations of the anisotropies in the cosmic microwave background. However, the current bounds on the scalar power spectrum over small scales are considerably weaker. During the last few years, there has been an interest in examining scenarios which generate enhanced scalar power on small scales and lead to significant production of primordial black holes as well as induce secondary gravitational waves (GWs) of possibly detectable amplitudes. In this talk, I shall first outline some of the inflationary scenarios we have examined in this context. Thereafter, I shall describe the scalar bispectrum arising in such scenarios in single field models of inflation and discuss the corresponding imprints on the spectral density of secondary GWs. I shall then illustrate the difficulty in generating enhanced power on small scales from squeezed initial states. Lastly, I shall highlight the manner in which non-trivial post-inflationary dynamics can leave telltale imprints on the spectral density of primary GWs at small scales.

12:00

Raghunath Pradhan Measurement of two-particle femtoscopic correlations in PbPb collisions with CMS detector
ABSTRACT The two particle correlations as a function of relative momenta of identified hadrons involving $\mathrm{K^{0}_{S}}$ and $\Lambda/\bar{\Lambda}$ are measured in PbPb collision at $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV with the data samples collected by the CMS experiment at the LHC. Such correlations are sensitive to the quantum statistics and possible final state interactions between the particles. The source radii are extracted from $\mathrm{K^{0}_{S}K^{0}_{S}}$ correlations in different centrality regions and found to decrease from central to peripheral collisions. The strong interaction scattering parameters are extracted from $\mathrm{K^{0}_{S}K^{0}_{S}}$, $\Lambda\mathrm{K^{0}_{S}}\oplus\bar{\Lambda}\mathrm{K^{0}_{S}}$, $\Lambda\Lambda\oplus\bar{\Lambda}\bar{\Lambda}$ and $\Lambda\bar{\Lambda}$ correlations using the Lednicky-Lyuboshits model, and compared with other experimental and theoretical results. In addition, we present results for the source radii of charged hadrons in peripheral PbPb collisions at $\sqrt{s_{_{\mathrm{NN}}}} =$ 2.76 TeV. The source radii in this case increase with event multiplicity, similar to those of identified hadrons.

12:15

Abhinash Sahu Quantum signatures of chaos in tomography of quantum states
ABSTRACT Does chaos in the dynamics enable information gain in quantum tomography or impedes it? We address this question by considering continuous measurement tomography in which the measurement record is obtained as a sequence of expectation values of a Hermitian observable evolving under the repeated application of the Floquet map of the quantum kicked top. For a given dynamics and Hermitian observables, we observe completely opposite behavior in the tomography of well-localized spin coherent states compared to random states. As the chaos in the dynamics increases, the reconstruction fidelity of spin coherent states decreases. This contrasts with the previous results connecting information gain in tomography of random states with the degree of chaos in the dynamics that drives the system. The rate of information gain and hence the fidelity obtained in tomography depends not only on the degree of chaos in the dynamics and to what extent it causes the initial observable to spread in various directions of the operator space but, more importantly, how well these directions are aligned with the density matrix to be estimated. Our study also gives an operational interpretation for operator spreading in terms of fidelity gain in an actual quantum information tomography protocol.

12:30

Suhail Ahmad Rather Dual-Unitary Gates and Absolute Maximal Entanglement
ABSTRACT Dual-unitary gates are maximally entangled bipartite unitary operators which are useful in quantum many-body physics and quantum information. In many-body physics these are used as building blocks of dual-unitary quantum circuits which serve as "solvable" quantum chaotic models. A particular subset of dual unitaries called as "2-unitaries" is in one-to-one correspondence with Absolutely Maximally Entangled (AME) states and perfect tensors with four indices. AME states are extremely correlated entangled quantum states which are crucial ingredients for quantum error-correcting quantum parallel teleportation, quantum secret sharing. In this talk I will give an overview of some of our recent vorks about the construction of dual-unitary operators, AME states and their relation to certain types of combinatorial designs.

13:00  - 16:00                   Lunch+Poster Session+Tea

SESSION 4 | CHAIR : Prof. K. Sethupathi

16:00

Prof. Vidya Praveen Defects in diamond for magnetic spectroscopy and quantum applications
ABSTRACT Dopants, essentially defects in otherwise pure material, play a crucial role in semiconducting electronic technology. Similarly, we are investigating the use of dopants and related defects in diamonds for use in nanoscale and quantum technologies. These defects are optically and spin active which enables a host of applications from nanoscale magnetic sensing to masing and single-photon emission. I will discuss the basic physics of these defects and their crucial properties that result in these applications. I will then discuss some recent advances my collaborators and I have made in NV-based spectroscopy.

16:30

Nasima Khatun Metal oxide – 2D Heterostructure materials for solar energy harvesting
ABSTRACT 2D materials have added new dimensions to both condensed matter physics and semiconductor devices. Also, metal oxides have a proven track record of the chemical and thermal stability, and ease of synthesis on the bulk scale that propelled several applications. Metal oxide nanostructures have shown immense potential in solar energy harvesting by minimizing recombination of photogenerated charges. However, for faster charge separation towards achieving better efficiency in photocatalysis, we have synthesized 1D metal oxide nanostructures functionalized by 2 D materials (g-C3N4, MXene etc). The talk will focus on some recent results from our research in this area.

16:45

Rajalekshmi T R Investigations on the near-white light emission, NIR emissions and lasing in Ga: LaCrO3
ABSTRACT The red and NIR emissions and exchange interactions observed due to Cr3+ ion when present in an oxygen environment makes it an interesting candidate for magnetic studies and optoelectronic applications. In this work, we observed a near-white light emission (near-WLE) and the selective tuning to the near-infrared (NIR) luminescence in Ga substituted lanthanum chromite (Ga: LaCrO3) perovskite with electron-beam excitation. The near-WLE observed in cathodoluminescence (CL) study, arises from the combination of 4T1(F) ?4A2 (blue), 4T1(P) ?4A2 (green) and 4T2?4A2 (red) spin allowed transitions and 2E?4A2 spin forbidden transitions from Cr3+. The spin allowed transitions from Cr3+ are not common, however can result by adjusting the Cr3+/Ga3+ concentration in the host lattice. The NIR emission originates from the selective 2E?4A2 transition, which dominates with the increasing concentration of Ga3+ ions. The Density Functional Theory (DFT) calculations point out the presence of extra electronic states with Ga substitution, which validates the observation of NIR emission in Ga substituted samples. Sharp lines were observed in the NIR emission spectrum for the LaCr0.5Ga0.5O3 sample on excitation with 488 nm laser. Further investigations reveal the presence of lasing due to the pair emission of Cr3+ ions in the system. The microcrystals present in the system work as suitable cavities for the lasing in the NIR region. The time-resolved photoluminescence (TRPL) spectrum of the sample has illustrated a sub-nanosecond lifetime and indicates 99% of the lifetime is contributed from the pair emission. The short lifetime can be attributed to a high concentration of Cr3+ ions, which enhances the Cr3+-Cr3+ exchange interaction and pair emission, and is evidenced by electron spin resonance study.

17:00

Saroj Kumar Barik Gas phase Formation of FeCN anion in the Interstellar medium
ABSTRACT The interstellar medium(ISM), is the vast space between the stars. Clouds of ISM consists of ions and neutral atoms/molecules, cluster, smaller and bigger dust particles. The chemical and physical processes that determine the ISM cloud dynamics are less probed. Despite the importance of negative ions in the ISM chemistry, only six negative molecular ions have been detected to date. In our lab, we probed the formation pathway of FeCN anion using the photoelectron velocity map imaging technique. A low-lying resonance of FeCN anion was identified. The non-Franck-Condon nature of the transition from resonance state to neutral ground state and the corresponding photoelectron angular distribution revealed that the resonance state is a dipole stabilised state. An unexpected active intramolecular vibrational energy redistribution (IVR) observed in FeCN anion suggests a competitive formation pathway of FeCN anion in the ground state over auto-detachment. In the talk, I will briefly discuss the experimental technique and results of the FeCN anion photoelectron spectroscopy experiment and the role of negative molecular ions in ISM chemistry.

17:15

Athrey C D Halide double perovskites- A novel class of materials with tunable structural, optical, and electronic properties through sublattice distortions
ABSTRACT Lead-free halide double perovskites is gaining significant attention as a stable and promising alternative to lead-halide perovskites owing to its exceptional structural stability and tunable optoelectronic properties. The idea of sublattice mixing in double perovskite to achieve desired physical properties are gaining significant interest. Specifically, the choice of B' and B" cations and halide anions (X= Cl, Br, I) in A2B'B"X6 structure dictates the sublattice distortions which can be effectively utilized to unfold various photophysical properties. In this talk, I will be discussing the influence of sublattice distortions resulting from alloying on the bandgap, self-trapped excitonic emissions and the electron-phonon coupling in double perovskites.
17:30 Anamika Ghosh

Design of non-precious metal catalyst for green H2 production by electrolysis of seawater

ABSTRACT The increasing consumption of fossil fuels has accelerated the urgent need to develop a strategy toward eco-friendly alternative-energy production. Hydrogen (H2) is the most desirable clean energy source due to its high gravimetric energy density (142MJ/kg). Production of H2 and O2 from water electrolysis is one of the simple and cost-effective approaches. However, water scarcity may arise if a vast amount of normal water is used for fuel production. Seawater, an abundant source that accounts for 96.5% of the total water resources, can be utilized for clean H2 production. While during seawater electrolysis, competitive chlorine evolution reaction is (CER) makes the overall reactions more sluggish. Considering the above-stated facts, the design of non-noble catalysts using a simple method for H2 and selective O2 production from the natural seawater is in high demand. The present work explores an assembly of transition metal-based Prussian blue analogue (PBA) type anode and metal encapsulated carbon shell for green H2 production from alkaline seawater. PBA's open framework type structure and available catalytically active metal sites enhanced the OER selectivity over CER. Finally, an electrolyzer with low overall seawater spilling voltage and long durability is demonstrated.
17:45 Dr. Avik Banerjee Real-time correlation functions of the Bjorken flow: gravitational Schwinger-Keldysh approach
ABSTRACT Computing real-time correlation functions away from the equilibrium stands out to be one of the most relevant, yet elusive problems in quantum many-body physics. In this context, the holographic (AdS/CFT) approach to strongly correlated many-body systems provide a considerable amount of analytic handle. In this talk, I will discuss the holographic computation of the Schwinger-Keldysh scalar correlation functions of the Bjorken flow, which describes the expanding plasma produced in heavy-ion collisions. I will explicitly demonstrate the Crossley-Gloriosso-Liu prescription for constructing the Schwinger-Keldysh contour in the bulk and how to extract the Schwinger-Keldysh propagator with our newly developed Matrix method. I will also show how our method elegantly reproduces various known results in this context.

18:00

Vote of thanks by Prof Dillip

19:00 onwards                  Dinner + Poster Session



 
Department of Physics - 2022