Department of Physics

&ldquo;IIT Jodhpur is committed to impart quality education to facilitate the creation of qualified, competent and responsible human resources to meet the emerging technological challenges of the world. It is working towards creating an equitable learning platform that is positive, accessible and effective in the face of the modern societal and scientific advancements.

Flexibility in curriculum, in all its academic programs, encompassing elements of teaching, research, creativity, innovation and entrepreneurship is the most unique feature of IIT Jodhpur. The Department of Science and Technology (DST), under the National Mission on Cyber Physical Systems, has identified IIT Jodhpur as a Technology &amp; Innovation Hub in the area of Augmented Reality and Virtual Reality. The institute has also been nominated as the coordinator for the Jodhpur City and Knowledge Cluster by the Office of Principal Scientific Adviser, Government of India.

The sprawling 852-acre IIT Jodhpur campus is a majestic tribute to the deep-rooted diverse cultural heritage of the region. The campus is an architectural masterpiece, which is slated to become an international exemplar of sustainability with net-zero energy, and advanced water and waste management strategies.&rdquo;

IIT Jodhpur

In this work, we study an important facet of field theories in curved space-time, viz. the Unruh effect, by making use of ideas of statistical mechanics and quantum foundations. Aspects of decoherence and dissipation, natural artifacts of open quantum systems, along with foundational issues such as the trade-off between coherence and mixing as well as various aspects of quantum correlations are investigated in detail for the Unruh effect. We show how the Unruh effect can be quantified mathematically by the Choi matrix approach. We study how environmentally induced decoherence modifies the effect of the Unruh channel. The differing effects of a dissipative or non-dissipative environment are noted. Further, useful parameters characterizing channel performance such as gate and channel fidelity are applied here to the Unruh channel, both with and without external influences. Squeezing, which is known to play an important role in the context of particle creation, is shown to be a useful resource in a number of scenarios. © 2017, The Author(s).

World University root node

Fulltext

Journal of High Energy Physics

Characterization of Unruh channel in the context of open quantum systems

Technological progress since the late twentieth century has centred on semiconductor devices, such as transistors, diodes and solar cells. At the heart of these devices is the internal motion of electrons through semiconductor materials due to applied electric fields or by the excitation of photocarriers. Imaging the motion of these electrons would provide unprecedented insight into this important phenomenon, but requires high spatial and temporal resolution. Current studies of electron dynamics in semiconductors are generally limited by the spatial resolution of optical probes, or by the temporal resolution of electronic probes. Here, by combining femtosecond pump-probe techniques with spectroscopic photoemission electron microscopy, we imaged the motion of photoexcited electrons from high-energy to low-energy states in a type-II 2D InSe/GaAs heterostructure. At the instant of photoexcitation, energy-resolved photoelectron images revealed a highly non-equilibrium distribution of photocarriers in space and energy. Thereafter, in response to the out-of-equilibrium photocarriers, we observed the spatial redistribution of charges, thus forming internal electric fields, bending the semiconductor bands, and finally impeding further charge transfer. By assembling images taken at different time-delays, we produced a movie lasting a few trillionths of a second of the electron-transfer process in the photoexcited type-II heterostructure - a fundamental phenomenon in semiconductor devices such as solar cells. Quantitative analysis and theoretical modelling of spatial variations in the movie provide insight into future solar cells, 2D materials and other semiconductor devices. © 2017 Macmillan Publishers Limited, part of Springer Nature.

Nature Nanotechnology

Imaging the motion of electrons across semiconductor heterojunctions

Transfer of electrons through semiconductor heterojunctions is the key process in all electronics. Here we make movies of electron dynamics in InSe/GaAs through time and spectrally-resolved photoemission electron microscopy, bringing insights to this fundamental process. © 2017 IEEE.

2017 Conference on Lasers and Electro-Optics, CLEO 2017 - Proceedings

Imaging electron motion in 2D semiconductor heterojunctions

Co-existence and interplay between mesoscopic light dynamics with singular optics in spatially disordered waveguide lattices is reported. Disorder induced singular behavior and diffusive wave propagation are quantitatively analyzed. © OSA 2017.

Optics InfoBase Conference Papers

Diffusive dynamics and signature of phase singularities in gain/loss assisted disordered optical waveguide lattices

We study methods of distinguishing the new physics operators which provide a good fit to the excess measured value of RD∗. Among the angular observables, we find that the D∗ polarization fraction fL(q2) is a good discriminant of scalar and tensor new physics operators. The change in hfL(q2)i, induced by scalar and tensor operators, is about three times larger than the expected uncertainty in the upcoming Belle measurement. © Copyright owned by the author(s).

Proceedings of Science

D∗ polarization as a probe to discriminate new physics in b¯ ↑ d∗τν¯

Detection of ultrahigh energy (UHE, 1 PeV) neutrinos from astrophysical sources will be a major advancement in identifying and understanding the sources of UHE cosmic rays (CRs) in nature. Long duration gamma-ray burst (GRB) blast waves have been considered as potential acceleration sites of UHECRs. These CRs are expected to interact with GRB afterglow photons, which are synchrotron radiation from relativistic electrons coaccelerated with CRs in the blast wave, and naturally produce UHE neutrinos. Fluxes of these neutrinos are uncertain, however, and crucially depend on the observed afterglow modeling. We have selected a sample of 23 long duration GRBs within redshift 0.5 for which adequate electromagnetic afterglow data are available and which could produce high flux of UHE afterglow neutrinos, being nearby. We fit optical, x-ray, and γ-ray afterglow data with an adiabatic blast wave model in a constant density interstellar medium and in a wind environment where the density of the wind decreases as the inverse square of the radius from the center of the GRB. The blast wave model parameters extracted from these fits are then used for calculating UHECR acceleration and pγ interactions to produce UHE neutrino fluxes from these GRBs. We have also explored the detectability of these neutrinos by currently running and upcoming large area neutrino detectors, such as the Pierre Auger Observatory, IceCube Gen-2, and KM3NeT observatories. We find that our realistic flux models from nearby GRBs will be unconstrained in the foreseeable future. © 2017 American Physical Society.

Physical Review D

Ultrahigh energy neutrino afterglows of nearby long duration gamma-ray bursts

Long duration Gamma Ray Bursts (GRBs) are well-motivated sources of Ultra High Energy Cosmic Rays (UHECRs) and neutrinos. During the afterglow phase these particles can be produced as a result of acceleration and interaction there in. We have modeled afterglow spectra and light curves from synchrotron cooling of accelerated electrons. We have fitted data of 17 long GRBs detected within redshift 0.5 in case of the GRB blastwave evolving in a wind and constant density interstellar medium. The afterglow photons can interact with the shock accelerated protons to produce very high energy neutrinos. We have calculated the neutrino flux for photo-pion interactions for all these GRBs. As IceCube have been detecting very high energy neutrinos for the last four years and a larger future extension called Gen 2 is planned, this calculation will help in understanding more about GRB neutrino production. Calculation of flux and estimation of events for Northern Hemisphere GRBs are done for the upcoming neutrino observatory KM3NeT. © Published under licence by IOP Publishing Ltd.

Journal of Physics: Conference Series

Very High Energy Neutrinos from nearby long GRB Afterglows

We use a multiscale simulation strategy to elucidate, at an atomistic level, the mechanisms underlying ion transport in the lamellar phase of polystyrene-polyethylene oxide (PS-PEO) block copolymer (BCP) electrolytes doped with LiPF6 salts. Explicitly, we compare the results obtained for ion transport in the microphase separated block copolymer melts to those for salt-doped PEO homopolymer melts. In addition, we also present results for dynamics of the ions individually in the PEO and PS domains of the BCP melt, and locally as a function of the distance from the lamellar interfaces. When compared to the PEO homopolymer melt, ions were found to exhibit slower dynamics in both the block copolymer (overall) and in the PEO phase of the BCP melt. Such results are shown to arise from the effects of slower polymer segmental dynamics in the BCP melt and the coordination characteristics of the ions. Polymer backbone-ion residence times analyzed as a function of distance from the interface indicate that ions have a larger residence time near the interface compared to that near the bulk of lamella, and demonstrates the influence of the glassy PS blocks and microphase segregation on the ion transport properties. Ion transport mechanisms in BCP melts reveal that there exist five distinct mechanisms for ion transport along the backbone of the chain and exhibit qualitative differences from the behavior in homopolymer melts. We also present results as a function of salt concentration which show that the mean-squared displacements of the ions decrease with increasing salt concentration, and that the ion residence times near the polymer backbone increase with increasing salt concentration. © The Royal Society of Chemistry 2017.

Soft Matter

Ion transport mechanisms in lamellar phases of salt-doped PS-PEO block copolymer electrolytes

Different approaches to synthesis of Li2FeSiO4-based electrode materials for lithium intercalation, using low-cost and abundant Li-, Si-, and Fe-containing parent substances, are discussed. XRD, SEM, and a laser-diffraction analyzer of particle size were used for structure and morphology characterization of the composite electrode materials. Li2FeSiO4 was shown to be the main lithium-accumulating crystalline phase; minor LiFeO2 and Li2SiO3 admixtures are also present. The material microparticles’ average size was shown to vary from tenths of micrometer to 1 μm. Larger objects sized ca. 2–4 μm are the microparticles’ agglomerates. The material electrochemical properties were studied by dc chronopotentiometry (galvanostatic charging–discharging) and cyclic voltammetry with potential linear sweeping. The initial reversible cycled capacity of the best samples is 170 mA h/g. The anodic and cathodic processes manifest obvious hysteresis caused by the presence of several different lithium ion energy states in the material; the transition between the states is kinetically hindered. The dependences of the specific capacity and its stability under cycling on the current load and the conductive carbon component content in the composite were elucidated. © 2017, Pleiades Publishing, Ltd.

Russian Journal of Electrochemistry

The synthesis, structure, and electrochemical properties of Li2FeSiO4-based lithium-accumulating electrode material

Thermal phase diagrams are computed for binary mixtures of different fatty acids with 1-dodecanol to design new eutectic phase change materials with melting temperatures and latent heatof fusion ranging from 15.5 to 19 °C and 183 to 188 kJ kg−1, respectively. The lauric (LA), myristic (MA) and palmitic (PA) fatty acids with 1-dodecanol eutectic compositions are identified and experimentally validated using differential scanning calorimetric measurements. The measured eutectic compositions are 29:71, 17:83, and 10:90 wt% for LA-DE, MA-DE, and PA-DE binary systems respectively. The melting temperatures and latent heat of fusion for these eutectic compositions are 17, 18.43, 20.08 °C and 175.3, 180.8, 191 kJ kg−1 respectively. The computed and measured composition weight fractions, melting temperature and latent heat of fusion values are in good agreement. The suitable melting temperature and considerably large latent heat of fusion for these designed and developed new eutectic phase change materials make them suitable for latent heat thermal energy storage systems for low temperature solar thermal applications such as building heating/cooling and body cooling clothing applications. © 2017 Elsevier Ltd

Solar Energy

Fatty acids/1-dodecanol binary eutectic phase change materials for low temperature solar thermal applications: Design, development and thermal analysis