Sumiran Pujari
Associate Professor
Photograph: 
Phone: 
(+91) 22-2576-9376
Email: 
sumiran@phy.iitb.ac.in
sumiran.pujari@iitb.ac.in
Fax Number: 
Sometimes I may not reply within a reasonable time period due to wrong spam filing by the institute email server if it sees it coming from a new email address. If there is such a suspicion, please write to my gmail with handle "first name dot last name".
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221 Physics

Research Interests: 
  • Condensed Matter Theory
  • Quantum Magnetism
  • Algorithms

Current group members:

  • Anoop Raj, Ph. D. candidate, 2022- -- Coulomb phases in classical dimer models
  • Sankalp Kumar, Ph. D. candidate, 2021- --  Quantum phase transitions in SU(N) magnets
  • Naba Prakash Nayak, Ph. D. candidate, 2019- -- Disorder driven quantum phase transitions (primarily supervised by Soumya Bera)

Past group members:

  • Vikas Vijigiri, Institute post-doc, 2021-2023  -- Deconfined criticality in S=1 Hamiltonians
  • Santanu Pal, Institute post-doc, 2019-2021 -- Colouring wavefunctions for quantum magnets
  • Saumitra Jain, Civil Engg., Ph.D., 2017-2022 -- Periodic Metamaterial based seismic isolation of structures (co-supervised with Arghadeep Laskar, Civil Engg.)
  • Tannistha Gupta, M. Phil exit, 2018-2022

Notable UG/PG collaborators:

  • Kilian Kuhlbrodt, M. Sc., 2022-2024 (ETH Zurich) and Adhyyan Mansukhani, B. Tech., 2021-2024 - Effect of magnetic fields on topological semimetals and superconductors
  • Vedant Motamarri, B.Tech+M.Tech, 2021-2022 -- Loop ensembles in Stochastic Series Expansion of Two-Dimensional Heisenberg Antiferromagnets
  • Abhishek Kejriwal, B.Tech+M.Tech, 2020-2023 -- Spin dynamics in Nitrogen vacancy centers in Diamond (co-supervised with Kasturi Saha, Elec. Engg.)
  • Sudipta Borah, M.Sc, 2020-2021 -- Study of edge modes in models with higher topological invariants
  • Vineet Punyamoorty, Elec. Engg., B.Tech+M.Tech, 2020-2021 -- Flux-flow Hall effect in superconductors using Time-Dependent Ginzburg-Landau Equations (co-supervised with Kasturi Saha, Elec. Engg.)

Extended past guest visitors:

  • Sept, 2024: Karlo Penc, Wigner Research Center, Budapest, Hungary.Lectures on spin-orbit coupling in Mott Insulators (available here). Some photos here.
  • Mar, 2019: Ribhu Kaul, Penn State University, USA (formerly University of Kentucky) Lectures on quantum spin chains. Some photos here.
Selected Publications: 
  • A general theorem on extensive ground state entropy in spin-1/2 models
    arXiv:2407.06236 
    A recent seminar video here that has some newer results on connections
    to Wegner's Z_2 Ising gauge theory from this year ("happiest thought"
    during my recent Jan-Mar 2025 stay at MPIPKS, Dresden!). Related older
    seminar video here or here, and slides here (Part II). The two-dimensional
    models discussed here appear to be a new beast in the zoo of strongly
    correlated phases and possibly outside the string-net kind of correlated
    phases of Levin-Wen models.

  • A class of exactly solvable Hamiltonians for S=1/2 quantum magnets
    with spinless fermionic excitations in higher dimensions,
    arxiv:2406.17034 
    Part of the proceedings of the 67th DAE Solid State Physics Symposium.
    Related slides here (Part I). Material/Artificial realization for
    this class of models with bond-dependent couplings seems feasible.
    Could be relevant to both classical spin-based technologies
    and artificial quantum technologies (for more discussion on this,
    see the preprint). The "unfrustrated XX" case seems to be a
    genuinely new state of matter where a classical spin liquid
    coexists with a quantum spin liquid. (also see arXiv:2407.06236)
  • Punctured-Chern topological invariants for semi-metallic bandstructures, 
    Phys. Rev. Lett. 130, 186202 (2023), arXiv:2205.07814
    Related slides here. These invariants could be useful for anyone interested
    in band topology in presence of gap-closing points.
  • Unusual spin dynamics in the low-temperature magnetically ordered state of Ag_3 Li Ir_2 O_6
    Phys. Rev. B 104, 115106 (2021), arXiv:2104.10057
    Related slides here that discuss the well-known (or perhaps little-known)
    issue about large muon relaxation rates in some ordered antiferromagnets
    (e.g. Gd_2 Sn_2 O_7 and also Ag_3 Li Ir_2 O_6) comparable to that of many
    spin liquid candidate materials.
  • Resummation-based quantum Monte Carlo for quantum paramagnetic phases
    Phys. Rev. B 104, L060406 (2021), arXiv:2104.06792
    Related seminar video here and slides here.
  • Bilayer Coulomb phase of two dimensional dimer models: Absence of power-law columnar order
    Phys. Rev. E 103, 042136 (2021), arXiv:2011.04506 
    Related seminar video here and slides here.
  • Gapless quantum spin liquid in the triangular system Sr_3 Cu Sb_ 2 O_9
    Phys. Rev. Lett. 125, 267202 (2020), arXiv:2012.01239 
    Related colloquium-style seminar video here and slides here.
  • Topological character of three-dimensional Nexus triple point degeneracies
    Phys. Rev. B 102, 235148 (2020),  arXiv:2006.00709 
    Related seminar video here and slides here.
    (a seminar video here and slides here on a previous work which was instrumental for this work.)
  • Resonating three-coloring wavefunctions for the kagome quantum antiferromagnet
    Phys. Rev. B 99, 104433 (2019), arXiv:1808.08633 
    Related seminar video here and slides here.
 
  • Interaction induced Dirac fermions in bilayer graphene
    Phys. Rev. Lett. 117, 086404 (2016), arXiv:1604.03876 
    Related slides here. (These slides contain unpublished results on SU(N>2) on-site
    Hubbard model on Bernal-stacked honeycomb bilayer, while the paper focused on
    SU(2). In short, for SU(4) there is a continuous quantum phase transition from a
    Dirac liquid to a Neél antiferromagnet similar to SU(2), while for SU(6) (and greater)
    there is a strong first-order transtion from the Dirac liquid to a valence bond solid.)
  • Sign-problem-free Monte Carlo simulation of certain frustrated quantum magnets
    Phys. Rev. Lett. 117, 197203 (2016), arXiv:1511.01586 
    Related slides here by F. Alet.
  • Transitions to valence-bond solid order in a honeycomb lattice antiferromagnet
    Phys. Rev. B 91, 104411 (2015), arXiv:1502.01035   
    Related slides here.
------------------------------------------- Puerile Ph.D. Phase ---------------------------------------------
 
  • Emergent spin excitations in a Bethe lattice at percolation
    Phys. Rev. Lett. 111, 157201 (2013), arXiv:1210.4621 
  • "Inversion" techniques for Scanning Tunneling Microscopy data analyses
    Ph. D. Thesis (2011)
    Related slides here and thesis document here.

Most of my publications are listed here.

A playlist of my talk videos is available here.

A few papers resulting through collaborations in the engineering discipline are not in this list.

Extended collaborations:

  • Sounak Biswas (2024-now, 2016-2017)
  • Fabien Alet (2024-now, 2011-2014 (as postdoc mentor))
  • Nisheeta Desai (2016-now)
  • Ankur Das (2018-2024)
  • Avinash Majahan (2018-2024)
  • Kedar Damle (2019-2020, 2016-2017 (as postdoc mentor), 2011-2014 (as postdoc mentor))
    (introduced as the "fifth member of the spin quartet" by R. Moessner here though
    unfortunately not part of the video. For the spin quartet reference, see here 
    around the 17 minute mark.)
  • Hitesh Changlani (2017-2021, 2008-2011)
  • Christopher Henley (2012-2013, 2006-2011 (as Ph.D. guide))

Other collaborators:

Old unpublished ideas:

  • Work on a Ladder representation for the Generalized Heisenberg
    Algebra [x̂, p̂] = i (1 + β(x̂ 2 + p̂ 2 )). An earlier version of this work
    has a section on "Unnatural Numbers" which may be of interest or
    amusement to some. 2015-16. Review exchange here.
  • Conjecture on an extension of the spontaneous symmetry 
    breaking idea from ordering to fluctuations. 2010-13. One of the
    "Happiest thoughts" of my life till now. This idea as it stands is 
    wrong due to a wrong assumption about the microscopic classical
    dynamics that happens during equilibration. Such dynamics
    may be allowed in dissipative, non-equilibrium systems in steady
    steady state. I thank Veit Elser, Jim Sethna, Deepak Dhar and
    Clement Sire for giving their time to me to discuss this work.

Teaching history:

  • 2023-24/1 PH 251 - Classical Mechanics (minor)
  • 2023, Tutor for summer school on the physics of quantum matter
  • 2021-22/2 PH 554 : Computational Many-body Physics
  • 2021-22/1 PH 217 : Classical Mechanics
  • 2021-22/2 PH 554 : Computational Many-body Physics
  • 2021-22/1 PH 401 : Classical Mechanics
  • 2020-21/2 PH 410 : Statistical Physics
  • 2020-21/1 PH 401 : Classical Mechanics
  • 2019-20/2 PH 438 : Statistical Physics
  • 2019-20/1 PH 217 : Classical Mechanics
  • 2018-19/2 PH 310 : Introduction to Condensed Matter Physics
  • 2018-19/1 PH 409 : Introduction to Condensed Matter Physics
  • 2017-18/2 EP 320 (now PH 438) Statistical Physics
  • 2017-18/1 PH 409 : Introduction to Condensed Matter Physics 

Miscellaneous:

  • a general talk video here given to IIT Bombay community on convocation-2020 speaker F. D. M. Haldane's Nobel prize winning work
  • slides on an outreach talk here on "Differential Equations in Science and Engineering" given at Sharad Chandra ACS College, Naigaon, Nanded, Maharashtra on Feb, 2020
  • my only published poem! The forgotten chapbook is avaiable here. Even received a cheque of ~15$ for the reading! which is now misplaced :( I would change a few things here and there in the poem now, but that's how it goes ...
    A video of the reading here; please excuse the cringe.
      some other writings here

Worldline:

  • 1983: Sambalpur, Odisha (birth, Prasanta Kumar Pujari (retired executive metallurgical engineer, RSP), Arundhati Pati (retired senior reader in Home Science)) 
  • 1983-2001: Rourkela, Odisha (childhood and schooling with Saswati Pujari)
  • 2001-2005: Mumbai (undergraduate)
  • 2005-2011: Ithaca, NY, USA (Ph.D. training)
  • 2011-2014: Toulouse, France (postdoc)
  • 2014-2016: Lexington, KY, USA (postdoc)
  • 2016-now: Mumbai
  • Summers of 2018,2019: Lexington, KY, USA (science + personal)
  • October of 2022: Bordeaux, France (science)
  • Winter of 2023: Trieste, Italy (science + visit)
  • June of 2024: Toulouse, France (science)
  • August of 2024: Bhubaneshwar, Odisha (science + personal)
  • Oct-Nov of 2024: Toulouse, France (science + travel)
  • Jan-Mar of 2025: Dresden, Germany (science + travel)
Research Category: 
Condensed Matter Theory