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<!doctype html><html><head> <meta charset="utf-8"> <meta name="keywords" content=""> <meta name="description" content=""> <meta name="viewport" content="width=device-width, initial-scale=1.0, viewport-fit=cover"><meta name="robots" content="index, follow" /> <link rel="shortcut icon" type="image/png" href="favicon.png"> <link rel="stylesheet" type="text/css" href="./css/bootstrap.min.css?4216"><link rel="stylesheet" type="text/css" href="style.css?6365"><link rel="stylesheet" type="text/css" href="./css/animate.min.css?9537"> <title>Projects-1</title> <!-- Analytics --> <!-- Analytics END --> </head><body><!-- Preloader --><div id="page-loading-blocs-notifaction" class="page-preloader"></div><!-- Preloader END --><!-- Main container --><div class="page-container"> <!-- bloc-0 --><div class="bloc none bgc-princeton-orange full-width-bloc" id="bloc-0"><div class="container bloc-sm bloc-no-padding-lg"><div class="row"><div class="col"><nav class="navbar navbar-light row navbar-expand-md" role="navigation"><a class="navbar-brand" href="index.html"><img src="img/logo.png" alt="logo" /></a><button id="nav-toggle" type="button" class="ml-auto ui-navbar-toggler navbar-toggler border-0 p-0" data-toggle="collapse" data-target=".navbar-21982" aria-expanded="false" aria-label="Toggle navigation"><span class="navbar-toggler-icon"></span></button><div class="navbar-content-area col"><h5 class="mg-lg float-lg-none h5-style tc-white">Indian Institute of Information Technology-Allahabad<br>भारतीय सूचना प्रौद्योगिकी संस्थान-इलाहाबाद<br></h5></div></nav></div></div></div></div><!-- bloc-0 END --><!-- bloc-1 --><div class="bloc l-bloc none" id="bloc-1"><div class="container bloc-sm bloc-no-padding-lg"><div class="row"><div class="col"><nav class="navbar row navbar-light navbar-expand-md" role="navigation"><button id="nav-toggle" type="button" class="ml-auto ui-navbar-toggler navbar-toggler border-0 p-0" data-toggle="collapse" data-target=".navbar-16243" aria-expanded="false" aria-label="Toggle navigation"><span class="navbar-toggler-icon"></span></button><div class="collapse navbar-collapse navbar-16243 col-lg-12"><ul class="site-navigation nav navbar-nav ml-auto"><li class="nav-item"><a href="index.html" class="nav-link ltc-black">Home</a></li><li class="nav-item"><a href="news.html" class="nav-link a-btn ltc-black">News</a></li><li class="nav-item"><a href="highlights.html" class="nav-link a-btn ltc-black">Highlights</a></li><li class="nav-item"><a href="people.html" class="nav-link a-btn ltc-black">People</a></li><li class="nav-item"><a href="publications_new.html" class="nav-link a-btn ltc-black">Publications</a></li><li class="nav-item"><a href="projects.html" class="nav-link a-btn ltc-black">Projects</a></li><li class="nav-item"><a href="research.html" class="nav-link a-btn ltc-black">Research</a></li><li class="nav-item"><a href="teaching.html" class="nav-link a-btn ltc-black">Teaching</a></li><li class="nav-item"><a href="online-tutorials.html" class="nav-link a-btn ltc-black">Online Tutorials</a></li><li class="nav-item"><a href="learning-resources.html" class="nav-link a-btn ltc-black">Learning Resourses</a></li><li class="nav-item"><a href="facilities.html" class="nav-link a-btn ltc-black">Facilities</a></li><li class="nav-item"><a href="outreach.html" class="nav-link a-btn ltc-black">Outreach</a></li></ul></div></nav></div></div></div></div><!-- bloc-1 END --><!-- bloc-2 --><div class="bloc bgc-dark-midnight-blue" id="bloc-2"><div class="container bloc-lg bloc-no-padding-lg"><div class="row"><div class="col"><h4 class="mg-md animDelay04 none animLoopInfinite h4-news--style animSpeedSlow animated fadeIn text-justify tc-white-2" data-appear-anim-style="fadeIn">News: Opening for SERB CRG JRF position. Click <a class="ltc-electric-yellow" href="downloads/Advt_JRF_sitangshu.pdf" target="_blank">here</a> from more information. Regular Ph.D. positions are advertised. Click <a class="ltc-electric-yellow" href="https://www.iiita.ac.in/downloads/announcements/uploads/FINAL%20Advertisement%20for%20PG_PhD%20Admission%20(2)891.pdf" target="_blank">here</a> for more details. </h4></div></div></div></div><!-- bloc-2 END --><!-- bloc-1 --><div class="bloc tc-black full-width-bloc" id="bloc-1"><div class="container bloc-lg bloc-sm-lg"><div class="row row-style"><div class="col-lg-12"><h4 class="mg-md text-lg-center mx-auto d-block tc-black">Electronic Structure Theory Group</h4></div><div class="col-12"><h5 class="mg-md text-lg-center tc-ferrari-red"><strong>Research Thrust Areas: Ab-initio calculations in two-dimensional materials </strong></h5></div></div></div></div><!-- bloc-1 END --><!-- bloc-6 --><div class="bloc l-bloc full-width-bloc" id="bloc-6"><div class="container bloc-lg bloc-sm-lg"><div class="row"><div class="col"><div ><title>HTML Ordered List</title> <ol><li style=" color:black;text-align:justify;line-height:2;><span style=" color:black;="" font-family:helvetica;"=""><i>Excitonic interplay with phonons in bulk and nanoscale semiconductor materials.</i> <br></li><li style=" color:black;text-align:justify;line-height:2;><span style=" color:black;="" font-family:helvetica;"=""><i>Quasi harmonic analysis like thermal zero point energy computations, temperautre dependent lattice constants, lattice anharmonicities.</i> <br></li><li style=" color:black;text-align:justify;line-height:2;><span style=" color:black;="" font-family:helvetica;"=""><i>Electrical mobilities in bulk and nanoscale semiconductor materials.</i> <br></li><li style=" color:black;text-align:justify;line-height:2;><span style=" color:black;="" font-family:helvetica;"=""><i>Nonlinear optical second and third harmonic generations in bulk and nanoscale semiconductor materials.</i> <br></li><li style=" color:black;text-align:justify;line-height:2;><span style=" color:black;="" font-family:helvetica;"=""><i>Pump-probe and fluences excitonic spectroscopy in bulk and nanoscale semiconductor materials.</i> <br></li><li style=" color:black;text-align:justify;line-height:2;><span style=" color:black;="" font-family:helvetica;"=""><i>Anamolous Hall effect, anisotropies from self-consistent Hubbard U in magnetic semiconductors and metals.</i> <br></li><li style=" color:black;text-align:justify;line-height:2;><span style=" color:black;="" font-family:helvetica;"=""><i>SMOKE and MOKE Kerr optical spectra from ferromagteic metals.</i> </li></ol></div></div></div></div></div><!-- bloc-6 END --><!-- bloc-58 --><div class="bloc full-width-bloc" id="bloc-58"><div class="container bloc-lg bloc-sm-lg"><div class="row"><div class="col"><h5 class="text-lg-center mg-clear tc-dark-green"><strong>Our Works on Calculating Optical Excitations in Famous 2D-Materials</strong></h5></div></div></div></div><!-- bloc-58 END --><!-- bloc-50 --><div class="bloc" id="bloc-50"><div class="container bloc-no-padding-lg"><div class="row"><div class="col-sm-8 offset-sm-2 offset-md-0 col-md-5 order-md-0 order-1 offset-lg-0 col-lg-7"><img src="img/lazyload-ph.png" data-src="img/exc.png" class="img-fluid mx-auto d-block lazyload" alt="placeholder image" /></div><div class="align-self-center col-md-7 offset-lg--1 order-lg-0 col-lg-5"><h1 class="mg-md text-center text-md-left h1-bloc-50-style tc-french-rose">Excitons in monolayers</h1><h3 class="mg-md float-none text-justify h3-bloc-50-style tc-bulgarian-rose">Excitonic transition weights on the bare electronic energy dispersions of NP monolayer. Bottom row: (d−f) resonant (R1, R2, and R3) excitonic transition weights on the bare electronic energy dispersions. The red areas correspond to the important vertical electronic transitions at the specific excitonic energy. The inset in each case exhibits the exciton weights in the Brillioun zone space. <a class="ltc-dark-green" href="https://pubs.acs.org/doi/pdf/10.1021/acs.jpcc.1c02091" target="_blank">Link</a><br></h3><div class="text-center text-lg-left text-md-left d-block"></div></div></div></div></div><!-- bloc-50 END --><!-- bloc-51 --><div class="bloc full-width-bloc" id="bloc-51"><div class="container bloc-sm-lg"><div class="row"><div class="col-sm-8 offset-sm-2 offset-md-0 col-md-5 order-md-0 order-1 offset-lg-0 col-lg-7"><img src="img/lazyload-ph.png" data-src="img/shg.png" class="img-fluid mx-auto d-block lazyload" alt="placeholder image" /></div><div class="align-self-center col-md-7 offset-lg--1 order-lg-0 col-lg-5"><h1 class="mg-md text-center text-md-left h1-bloc-50-style tc-french-rose">Optical second harmonic generations: Time-dependent BSE</h1><h3 class="mg-md float-none text-justify h3-bloc-50-style tc-bulgarian-rose">Nonlinear SHG spectra of ML buckled GaAs as function of laser frequencies. Panels (a, c, and e) are the SHG computed using IPA+scissor, TD-DFT, and TD-BSE level of theory, respectively (all are respective absolute values). Panels (b, d, and f) show the absorption spectra computed at ω and ω/2 under the IPA+scissor, TD-DFT, and TD-BSE level of theory, respectively. The open circles are the experimental SHG spectra of zincblende bulk GaAs taken from Bergfeld and Daum and put here for comparison with our monolayer structure. The solid and dashed vertical lines are for the ω and ω/2 gaps. The imaginary and real parts for each of the theory are also presented. From the imaginary part, one can see that SHG goes to zero below half of the band-gap in all the cases. All of these computations were performed on 72×72×1k-point grid. <a class="ltc-dark-green" href="https://journals.aps.org/prb/abstract/10.1103/PhysRevB.101.155132" target="_blank">Link</a><br></h3><div class="text-center text-lg-left text-md-left d-block"></div></div></div></div></div><!-- bloc-51 END --><!-- bloc-52 --><div class="bloc full-width-bloc" id="bloc-52"><div class="container bloc-sm-lg"><div class="row"><div class="col-sm-8 offset-sm-2 offset-md-0 col-md-5 order-md-0 order-1 offset-lg-0 col-lg-7"><img src="img/lazyload-ph.png" data-src="img/thg_np.png" class="img-fluid mx-auto d-block lazyload" alt="placeholder image" /></div><div class="align-self-center col-md-7 offset-lg--1 order-lg-0 col-lg-5"><h1 class="mg-md text-center text-md-left h1-bloc-50-style tc-french-rose">Optical third harmonic generations: Time-dependent BSE</h1><h3 class="mg-md float-none text-justify h3-bloc-50-style tc-bulgarian-rose">Nonlinear THG spectra of monolayer NP as function of laser frequencies exhibiting the peaks C1, C2, and C3 and C1′, C2′, and C3′ due to the bound excitons B1, B2, and B3 and the resonant exciton R1, R2, and R3, respectively. The x axis is the laser frequency. (b) Absorption spectra at ω and ω/3 under the same TD-BSE level of theory. The vertical dashed line exhibits the ω/3 gap. One can see that χ^(3) goes to zero below one-third of the gap. <a class="ltc-dark-green" href="https://pubs.acs.org/doi/pdf/10.1021/acs.jpcc.1c02091" target="_blank">Link</a><br></h3><div class="text-center text-lg-left text-md-left d-block"></div></div></div></div></div><!-- bloc-52 END --><!-- bloc-51 --><div class="bloc" id="bloc-51"><div class="container bloc-sm-lg"><div class="row"><div class="col-sm-8 offset-sm-2 offset-md-0 col-md-5 order-md-0 order-1 offset-lg-0 col-lg-7"><img src="img/lazyload-ph.png" data-src="img/phonon_BN.png" class="img-fluid mx-auto d-block lazyload" alt="placeholder image" /></div><div class="align-self-center col-md-7 offset-lg--1 order-lg-0 col-lg-5"><h1 class="mg-md text-center text-md-left h1-bloc-50-style tc-french-rose">Density Functional Perturbation Theory</h1><h3 class="mg-md float-none text-justify h3-bloc-50-style tc-bulgarian-rose">Temperature dependent studies on optical or electronic spectra can be well studied by assessing electron-phonon self energies. These self-energies commonly known as Fan (first order) and Debye-Waller (second order) self-energies and are evaluated from density functional perturbation theory. Image shows Eliashbeg function of monolayer BN. <a class="ltc-dark-green" href="https://journals.aps.org/prb/abstract/10.1103/PhysRevB.99.165201" target="_blank">Link</a></h3><div class="text-center text-lg-left text-md-left d-block"></div></div></div></div></div><!-- bloc-51 END --><!-- bloc-51 --><div class="bloc" id="bloc-51"><div class="container bloc-sm-lg"><div class="row"><div class="col-sm-8 offset-sm-2 offset-md-0 col-md-5 order-md-0 order-1 offset-lg-0 col-lg-7"><img src="img/lazyload-ph.png" data-src="img/QP_GW.png" class="img-fluid mx-auto d-block img-style lazyload" alt="placeholder image" /></div><div class="align-self-center col-md-7 offset-lg--1 order-lg-0 col-lg-5"><h1 class="mg-md text-center text-md-left h1-bloc-50-style tc-french-rose">Self-Consistent GW Theory</h1><h3 class="mg-md float-none text-justify h3-bloc-50-style tc-bulgarian-rose">The dynamic long range electron-electron correlation is responsible for opening the quasi-particle electronic energy gap or simply the G0W0 gap. This essential “salt” is missing in density functional theory that leads to gap underestimation. Image is for GW corrections done on monolayer WSe2. <a class="ltc-dark-green" href="https://journals.aps.org/prb/abstract/10.1103/PhysRevB.98.045143" target="_blank">Link</a><br></h3><div class="text-center text-lg-left text-md-left d-block"></div></div></div></div></div><!-- bloc-51 END --><!-- bloc-52 --><div class="bloc" id="bloc-52"><div class="container bloc-sm-lg"><div class="row"><div class="col-sm-8 offset-sm-2 offset-md-0 col-md-5 order-md-0 order-1 offset-lg-0 col-lg-7"><img src="img/lazyload-ph.png" data-src="img/exciton_Wse2.png" class="img-fluid mx-auto d-block img-style lazyload" alt="placeholder image" /></div><div class="align-self-center col-md-7 offset-lg--1 order-lg-0 col-lg-5"><h1 class="mg-md text-center text-md-left h1-bloc-50-style tc-french-rose">Optical Absorption Spectra: Bethe-Salpeter Equation</h1><h3 class="mg-md float-none text-justify h3-bloc-50-style tc-bulgarian-rose">First principles calculations based on the solution of the many-body GW and Bethe-Salpeter equation (BSE) are now a days the most reliable theoretical approach to investigate particle-hole dynamics in crystals. Essentially, the peaks in the photoluminescence spectrum with energy below the gap correspond to bound state electron-hole pairs, known as excitons. Image is for temperature dependent oscillator strength done on monolayer WSe2. <a class="ltc-dark-green" href="https://journals.aps.org/prb/abstract/10.1103/PhysRevB.98.045143" target="_blank">Link</a><br></h3><div class="text-center text-lg-left text-md-left d-block"></div></div></div></div></div><!-- bloc-52 END --><!-- ScrollToTop Button --><a class="bloc-button btn btn-d scrollToTop" onclick="scrollToTarget('1',this)"><svg xmlns="http://www.w3.org/2000/svg" width="22" height="22" viewBox="0 0 32 32"><path class="scroll-to-top-btn-icon" d="M30,22.656l-14-13-14,13"/></svg></a><!-- ScrollToTop Button END--><!-- bloc-4 --><div class="bloc bgc-black l-bloc" id="bloc-4"><div class="container bloc-sm-lg"><div class="row bgc-black"><div class="col bgc-black"><h1 class="mg-md h1-style text-lg-center tc-electric-yellow">Website developed by Dr. Sitangshu Bhattacharya, ECE, IIITA (<i>sitangshu</i>[at]iiita.ac.in). Copyright@2021 Indian Institute of Information Technology-Allahabad, Uttar Pradesh 211 015, India</h1></div></div></div></div><!-- bloc-4 END --></div><!-- Main container END --> <!-- Additional JS --><script src="./js/jquery.min.js?2609"></script><script src="./js/bootstrap.bundle.min.js?9687"></script><script src="./js/blocs.min.js?670"></script><script src="./js/lazysizes.min.js" defer></script><!-- Additional JS END --></body></html>