Antimonene Project

  • Master's thesis Phase II work on transport study and characterization of a novel 2D material, Antimonene

    Supervisor: Professor Suddhasatta Mahapatra, Department of Physics, IIT Bombay

    January, 2018 - June, 2018  

    Antimonene is to Antimony what Graphene is to Carbon. With its hexagonal honeycomb lattice, it is theoretically predicted to exhibit topological phase transitions as the number of monolayers of the antimonene decreases, going from a semi-metal to a topological insulator to a quantum spin hall insulator and finally a bandgap insulator when there are only about 2-3 monolayers.  

    We fabricated the antimonene layers and in this project, characterized the material to determine whether its antimonene and its structure and then made designs for design fabrication for carrying out electron transport and hall measurements. 

Thesis Report_Vaibhav (pdf)

Download

Antimonene_PPT (pdf)

Download

Quantum Antiferromagnetism

  • Research project on quantum antiferromagnetism by exploring model hamiltonians on a Kagome Lattice with Heiseberg Antiferromagnetic Exchange Interactions.

    Supervisor: Professor Sumiran Pujari, Department of Physics, IIT Bombay

    Professor Hitesh Changlani, Department of Physics, Florida State University

    August, 2017 -  June, 2018

    Explored the ground state of the system in the 3-coloring Hilbert space and calculated spin-spin correlations and spin structure factors in different total spin and topological sectors.

    Exact diagonalized the Rokhsar-Kivelson type model hamiltonian on the Kagome lattice of size 3X3, 4X4 and 5X5 to study the ground state of the system and whether it is ordered or spin liquid.  

Proximity Superconductivity Effect

  • Master's thesis phase I project on probing the proximity superconductivity effect in Galium Nitride (GaN) nanowires.

    Supervisor: Professor Suddhasatta Mahapatra, Department of Physics, IIT Bombay

    July, 2017 - December, 2017

    GaN nanowires when kept between two superconducting contacts below the critical temperature of the superconductors can support supercurrents through the phenomenon of Andreev reflection.

    Since GaN is a semiconductor, it is easy to alter its charge carrier density using a gate voltage. Altering the charge carrier density can switch the supercurrent on and off in this proximity superconductivity effect and thus it can be used as a switch.

    The project involved fabricating devices from these GaN nanowires and lead superconducting contacts on a Silicon-Silicon Dioxide substrate using Focussed Ion Beam Machining and making low temperature transport measurements. 

Thesis Report_Vaibhav (pdf)

Download

Thesis Presentation (pdf)

Download

X Ray Diffraction Line Profile Analysis

Analysed the line profiles of the X-ray diffraction patterns of GeSn epilayers and obtained a fitting formula using kinematic scattering to accurately determine dislocation densities in the epilayer.

Supervisor: Professor Sudhasatta Mahapatra, Department of Physics, IIT Bombay

December, 2016 - July, 2017

GeSn epilayers are one way of realizing direct band-gap in silicon and silicon like materials for photonics applications due to the alloying of tin.

In making these epilayers, it is vital to know how much defects they have in terms of dislocation densities. The standard way to determine it is by counting in a Transmission Electron Microscopy scan but this physical counting is not accurate since it extrapolates the dislocations i a few patches to the whole layer.

A more accurate method is to use the X ray diffraction pattern of the whole layer since the broadening of the diffraction peaks are determined by the dislocations.

We used the method developed by Kaganer et al for hexagonal close packed structures for our cubic lattice system to to obtain a fitting formula for our x ray diffraction peaks and obtained accurate estimates of the dislocation density. I built a MATLAB based fitting tool which then fit ou x ray peaks accurately.

The results of this work were used in two publications linked below:
Publication 1

Publication 2

Measuring Rare B-meson decays for new physics

  • Inclusive Measurement of rare B-meson decays from LHC data using machine learning techniques to probe physics beyond the standard model.  

    Supervisor: Dr. Konstantinos Petridis, Department of Physics, University of Bristol

    May, 2017 - July, 2017

    B-meson decays at loop level are suppressed by Standard model and are thus rare decays. Thus these decays are ideal to probe for new physics since known standard model physics won't wash out the teeny new physics results if any.

    The issue with measuring a particular (exclusive) B meson decay channel is that the theoretical predictions from standard model for such a decay are themselves having big error bars. However, if all possible decay channels are taken into account (inclusive), the error bars in theory are smaller and thus decay rates can be compared from theory and experiment to see new physics if present.

    I used machine learning techniques like Boosted Decision Trees to separate the inclusive B meson decays from the large background signals in the LHC data.

Presentation (pdf)

Download

Active Galactic Nuclei

  • Verification of the current unification model of Active Galactic Nuclei (AGN) from X-ray observation data

    Supervisor: Professor Vikram Rentala, Department of Physics, IIT Bombay

    January, 2017 - May, 2017

    AGNs that have been discovered seem to show different properties. Some AGNs have radio jets emanating out of them while some do not have that feature. To account for these differences, one theory is that it is only due to us seeing AGNs in different orientations.

    Thus, the AGNS with radio jets, called Type 1 are ones which are face-on with respect to the Earth while the ones without radio jets (Type II) are edge-on with respect to the Earth.

    We tried to test this using another means. Most AGNs have accretion disks and emit radiation of all wavelengths due to it being very hot. It emits in the X-ray region and it emits a signature iron K alpha line due to reprocessing in the accretion disk.

    For unobscured type 1 AGNs, the iron k alpha lines should be more prominent and the covering factor (absorption) should be less as compared to type 2 AGNs.

    We took a sample of AGN data from the NuSTAR satellite and determined if the classification fits these tests by analyzing data using the HEAsoft XSPEC software.

    Our sample was small but we found that this classification was weak as some type 2 AGNs showed broader iron k alpha lines than type 1. 


Final Report (pdf)

Download

Presentation (pdf)

Download

Reading Project on High Pressure Effects in Superconductors

  • A literature review and summary of how high pressure affects superconductivity in conventional and high temperature superconductors.

    February, 2018 - April, 2018

High_Pressure__Effects_in_Superconductors_Vaibhav (pdf)

Download

Reading project on laser induced breakdown spectroscopy

  • Reading project on the principle of laser induced breakdown spectroscopy, its technology and applications.

    September, 2017 - November, 2017

Report_LIBS (pdf)

Download

Course project on Cuprates & High Temp Superconductivity

  • Presentation on summarizing the current experimental and theoretical understanding of high temperature superconductivity in cuprates.

    January, 2018 - April, 2018

HTSC_ppt (pdf)

Download