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".
Office: 

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:

  • 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
  • Santanu Pal, Institute post-doc, 2019-2021 -- Colouring wavefunctions for quantum magnets
  • Vikas Vijigiri, Institute post-doc, 2021-2023  -- Deconfined criticality in S=1 Hamiltonians

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.)
Selected Publications: 
  • A general theorem on extensive ground state entropy in spin-1/2 models
    arXiv:2407.06236
    Related seminar video here.
    The two-dimensional model discussed here appears 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.

  • 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. 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)

  • Deconfined pseudocriticality in a model spin-1 quantum antiferromagnet,
    arXiv:2307.14254
    Related slides here. Rejected by PRL and PRBL. Offered PRB.
    (Review exchange at this link; names and accession code redacted)
  • 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 at : https://arxiv.org/a/pujari_s_1.html

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

Extensive collaborations:

  • Ankur Das (2018-now)
  • Nisheeta Desai (2016-now)
  • Avinash Majahan (2018-now)
  • 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 past 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 
    idea from ordering to fluctuations. 2010-13. This idea 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
  • some other writings here

Worldline:

Research Category: 
Condensed Matter Theory