Faculty at School of Natural Sciences

Subhra Sen Gupta

Subhra Sen Gupta

Assistant Professor

School of Natural Sciences


Contact Information

The research in our group can be broadly classified as Theoretical Condensed Matter Physics. More specifically, our research focuses on the field of  Strongly Correlated Electron Systems (Ground State as well as Spectroscopic properties), where electron-electron interactions cannot be treated as a perturbation to its motion in the crystal potential, resulting in the breakdown of conventional band-structure description for such systems, at least in the rigourous sense.

On one hand, this field helps us to better understand emergent phenomena that can arise out of strong, non-perturbative interactions between electrons in narrow-band solids, like compounds of transition metals, rare-earths and actinides. The hallmark of this is seen in exotic phenomena like colossal magnetoresistance in the Manganites, high-temperature superconductivity in the Cuprates, spin-charge separation and charge fractionalization in low-dimensional correlated systems, and the Kondo effect, to name a few. In such phenomena one simply cannot think of each electron independently, but must take into account the collective behaviour of a macroscopically large number (~ Avogadro's Number) of electrons, all acting in unison. On the other hand, a basic understanding of the physics of these materials helps in designing “smart materials” with advanced and energy-efficient functionalities.

Since treating the full correlation problem for an infinite solid is an unsolvable problem, the challenge for theory is to continuously develop newer and more efficient analytical approximations and numerical techniques to better understand the properties of these “quantum materials”, as constantly emerging from experiments. We have been working in this field for more than a decade, trying to model the ground state (low-energy) as well as the spectroscopic (high-energy) properties of correlated electron systems, in collaboration with leading experts in the field, both in India and abroad. We are interested both in model problems as well as in complex real materials. Our research interests and efforts have been traditionally directed towards the following broad areas :

  • Electronic, Magnetic and Spectral properties of Strongly Correlated Electron Systems : Including mixed-valent systems, systems with strong spin-orbit coupling (e.g., 4d and 5d transition metal oxides), systems exhibiting exotic spin-orbital and hidden order.
  • Modeling of high-energy X-ray spectroscopies : e.g. XAS, AES, XPS, NIXS, RIXS etc. in strongly correlated systems.
  • Spin/orbital magnetism and magneto-crystalline anisotropy in nano-structured materials : e.g., surfaces/thin-films/multilayers/nano-particles etc.
  • Development of new computational tools for correlated electron systems.

More recently, we have developed an interest in some newer research areas and are already pursuing active research in some of them (highlighted in blue). These are listed below :

  • Calculation of High-energy Optical Conductivity in Strongly Correlated Electron Systems (related to my successfully completed DST Project ECR/2016/002054).
  • Application of Random Matrix Theory (RMT) to Disordered Quantum Electronic and Spin Systems.
  • Integrability, Ergodicity and Quantum Chaos in Quantum Lattice Models.
  • Multifractality and Many-body Localization in Disordered Interacting Systems.
  • Investigation of Astrophysical Magnetism in Compact Astrophysical Objects based on Methods of Quantum Statistics.
  • Topological Aspects in Condensed Matter Physics.

TEACHING :

I love teaching and am open to teaching almost any Core course and designing new Electives. Since January 2015, I have taught the following courses at SNU :

  • PHY102 : Introduction to Physics II, Laboratory (Under-graduate Core). [Spring 2015]
  • PHY203 : Introduction to Mathematical Physics I (Under-graduate Core). [Monsoon 2017, 2018]
  • PHY304 : Condensed Matter Physics (Under-graduate Core). [Spring 2015, 2016 & 2021]
  • PHY305 : Quantum Mechanics I (Under-graduate Core). [Monsoon 2015-2020]
  • PHY306 : Quantum Mechanics II (Under-graduate Core). [Spring 2016-2022]
  • PHY417 : Topics in Quantum Many Body Theory  (Under-graduate Advanced Elective, Suitable for Post-Graduates too). [Spring 2017-2018, Monsoon 2019-2021]
  • PHY508 : Review of Quantum Mechanics (Post-graduate Core). [Monsoon 2015]
  • PHY507 : Review of Statistical Mechanics (Post-graduate Core). [Monsoon 2023]
  • CCC 422 : Demystifying the Strange Quantum World for the Layman [Spring 2020 (2 batches), Monsoon 2021 (one batch), Spring 2022 (two batches)]
  • PHY301 : Classical Mechanics (Under-graduate Core). [Monsoon 2021, Monsoon 2022]
  • PHY101 : Introduction to Physics – 1, Lectures (Under-graduate Core, Service Course for Engineering). [Monsoon 2022]
  • PHY102 : Introduction to Physics – 2, Lectures (Under-graduate Core, Service Course for Engineering). [Spring 2023]
  • PHY499 : Undergraduate Thesis(4th Year) (Under-graduate Core, as Thesis Supervisor, Examiner, Thesis Evaluator).
  • PHY599 : Research Methodology (Post-Graduate CORE, Instructor).

DOCTORAL RESEARCH STUDENTS :

  • Debojyoti Kundu (Presented Synopsis and Submitted Synopsis Report)
  • Irfan Nazir Mir (1st Year)

UNDERGRADUATE RESEARCH STUDENTS :

I. UNDERGRADUATE THESIS

2023-2024 [Graduating in 2024]

  • Amrita Ahuja (Grade : Awaited).
  • Jasmehar Chawla (Grade : Awaited).

2019-2020 [Graduated 2020]

  • Kartikeya Rambhatla (Grade : A-).

2018-2019 [Graduated 2019]

  • Vikas S. Bhat (Grade : A-, Pursuing Integrated Ph.D. at TIFR, Mumbai).
  • Ninaad Adhvaryu (Grade : A-, About to start Masters in Physics at University of Stuttgart, Germany.)

2017-2018 [Graduated 2018]

  • Siddharth Seetharaman (Grade : A, Pursuing Ph.D. at Ohio State University, USA).
  • Girish Kumar (Grade : A-, Pursuing Masters in Astrophysics at University of Amsterdam, The Netherlands).
  • Prakriti Kayastha (Grade : A-, Pursuing Ph.D. at TIFR, Hyderabad).

II. OPPORTUNITIES FOR UNDERGRADUATE RESEARCH (OUR)

2022-2023

  • Arvind Vinod

2021-2022

  • Akshat Pandey

  • 2007 Doctor of Philosophy (Ph.D.) [Specialization : Theoretical Condensed Matter Physics], Indian Institute of Science (IISc), Bangalore, India (Integrated Ph.D. Program).
  • 2000 M.S. (Physical Sciences), Indian Institute of Science (IISc), Bangalore, India (Integrated Ph.D. Program).
  • 1997 B.Sc. (Physics Hons.), St. Xavier’s College, Kolkata, India (University of Calcutta).

  • 12/14 – Present -Assistant Professor, Department of Physics, School of Natural Sciences, Shiv Nadar University and then auto-transferred to the Shiv Nadar IoE, Delhi-NCR.
  • 01/13 - 12/14 - RIKEN FPR (Foreign Postdoctoral Researcher) Fellow, RIKEN (Computational Condensed Matter Physics Laboratory, ASI/CEMS), Wako, Japan.
  • 03/12 - 12/12 - Visiting Research Associate, Department of Condensed Matter Physics and Material Science, S.N. Bose National Centre for Basic Sciences, Kolkata, India.
  • 03/08 - 02/12 - Post-doctoral Research (and Teaching) Fellow, Department of Physics & Astronomy, University of British Columbia (UBC), Vancouver, BC, Canada.
  • 01/07 - 02/08- Postdoctoral Fellow, Department of Material Science, S. N. Bose National Centre for Basic Sciences, Kolkata, India.

Early Career Research Award (ECRA) Grant of SERB (DST) [3-year budget of ~ 21 Lakhs], India, ECR/2016/002054, (2018-2021). Research Grant of ? 1,000,000 per year (for 3 years) as a part of the RIKEN FPR Fellow Position at the RIKEN Wako Institute, Japan (2013-2016).

  • 2023  Chosen by SN IoE to be the Convenor and Moderator for the Panel Discussion : “The Indo-French Cooperation Perspectives in Quantum Technology”, featuring the famous French Nobel Laureate, Prof. Serge Haroche, and three other National Experts on the subject, during Prof. Haroche’s visit to SN IoE (Held on 13 February, 2023).
  • 2023  Invited Speaker at the National Conference : “8th Indian Statistical Physics Community Meeting (ISPCM-2023)” held at TIFR-ICTS, Bangalore (February, 2023).
  • 2022  Invited Speaker and Session Chair at the International Conference “6th Young Investigators Meet on Quantum Condensed Matter Theory (YIMQCMT-2022)" organized by NISER, Bhubaneshwar, during October-November, 2022.
  • 2022   Invited Speaker and Co-organizer of the the National Conference : “d-d Transitions : A Discussion Meeting on the Electronic Structure of Materials” held at Colva, Goa (August, 2022).
  • 2021   Invited Speaker at the International Conference “5th Young Investigators Meet on Quantum Condensed Matter Theory (YIMQCMT-2021)" organized by NISER, Bhubaneshwar, during November, 2021.
  • 2021 Invited Speaker at the International Conference “Interdisciplinary Topics in Advanced Materials (ITAM-2021)” organized jointly by IISc and JNCASR, Bangalore during July, 2021
  • 2019NORDITA Academic Visitor in the Astrophysics Group of Nordic Institute for Theoretical Physics (NORDITA), Stockholm, Sweden (June, 2019).
  • 2016  Early Career Research Award, SERB (DST), India.
  • 2012Selected for the prestigious RIKEN Foreign Postdoctoral Researcher (FPR) Fellowship, RIKEN, Japan (about 20 candidates selected Internationally every year, including the fields of Physics, Chemistry, Biology, Medicine and Engineering)
  • 2007                       Spontaneously offered a Post-doctoral Position in the renowned Sawatzky Group, at the University of British Columbia, Vancouver, Canada, after receiving a exceptionally good Ph.D. Thesis Report from Prof. G. A. Sawatzky, a father figure in the field.
  • 1997  Selected for the Integrated Ph.D. Fellowship/Program of the Indian Institute of Science, Bangalore, India. Followed by the IISc JRF and SRF Fellowships in 1999 and 2002.
  • 1997   National Merit Scholar (1997) (Govt. of India) on the basis of B.Sc. (Hons.) results.
  • 1994   National Merit Scholar (1994) (Govt. of India) on the basis of XII std. results (ranked 40th in the State of West Bengal).

  • Received Rs. 30,000 as the OUR Grant as a part of of Approved OUR Project “Using Quantum Mechanics to understand Quantum Information and Quantum Entropies.” (2022-23).
  • Early Career Research Award (ECRA) Grant of SERB (DST) [3-year budget of ~ 21 Lakhs], India, ECR/2016/002054, (2018-2021). [Status : Closed Successfully in December 2022]
  • Research Grant of ¥ 1,000,000 per year (for 3 years) as a part of the RIKEN FPR Fellow Position at the RIKEN Wako Institute, Japan (2013-2016). 

  • Next-Nearest Neighbor Spacing Distribution Studies in a Variety of  Single-body and Many-body Quantum Chaotic Models :  Debojyoti Kundu, Santosh Kumar*, Subhra Sen Gupta* (Submitted to Phys. Rev. B, 2023).
  • Signatures of spectral crossovers in the short- and long-range spectral correlations of a disordered spin-chain with Kramers degeneracy : Debojyoti Kundu, Santosh Kumar*, Subhra Sen Gupta*, Phys. Rev. B 107, 094205 (2023).
  • Spectral Crossovers and Universality in Quantum Spin-chains Coupled to Random Fields : Debojyoti Kundu, Santosh Kumar*, Subhra Sen Gupta*, Phys. Rev. B 105, 014205 (2022).
  • RMT Spectral Distribution Crossovers in Random Spin Chains, Debojyoti Kundu, Santosh Kumar, Subhra Sen Gupta, Bulletin of the American Physical Society (2021).
  • Coexistence of Bound and Virtual-bound States in Shallow-core to Valence X-ray Spectroscopies : Subhra Sen Gupta*, J. A. Bradley, M. W. Haverkort, G. T. Seidler, A. Tanaka, and G. A. Sawatzky, Phys. Rev. B 84, 075134 (2011).
  • The Importance of Inter-site Coherences in the X-ray Absorption Spectra of Mixed-valent Systems : Subhra Sen Gupta*, Hiroki Wadati and G. A. Sawatzky, Europhysics Letters 93, 47008 (2011).
  • Probing electronic correlations in actinide materials using multipolar transitions : J. A. Bradley, Subhra Sen Gupta, G. T. Seidler, K. T. Moore, M. W. Haverkort, G. A. Sawatzky, S.D. Conradson, D. L. Clark, S. A. Kozimor, and K. S. Boland, Phys. Rev. B 81, 193104 (2010).
  • Supramolecular control of the magnetic anisotropy in two-dimensional high-spin Fe arrays at a metal interface : P. Gambardella, S. Stepanow, A. Dmitriev, J. Honolka, Frank de Groot, M. Lingenfelder, Subhra Sen Gupta, D. D. Sarma, P. Bencok, S. Stanescu, S. Clair, S. Pons, N. Lin, A. P. Seitsonen, H. Brune, J. V. Barth and K. Kern, Nature Materials (Letters) 8, 189 (2009).
  • Theory of the unusual doping and temperature dependence of photoemission spectra in manganites: Prabuddha Sanyal, Subhra Sen Gupta, Nandan Pakhira, H. R. Krishnamurthy, D. D. Sarma and T. V. Ramakrishnan, Europhysics Letters 82, 47010 (2008).
  • Spin-flop ordering from frustrated ferro- and antiferromagnetic interactions : A combined theoretical and experimental study of a Mn/Fe(100) monolayer : C. Grazioli, D. Alfe, S.R. Krishnakumar, Subhra Sen Gupta, M. Veronese, S. Turchini, N. Bonini, A. Dal Corso, D. D. Sarma, S. Baroni and C. Carbone, Phys. Rev. Lett. 95, 117201 (2005).
  • X-ray absorption spectroscopy of transition-metal doped oxide diluted magnetic semiconductors Zn1-xMxO : J. Okabayashi, K. Ono, M. Mizuguchi, M. Oshima, Subhra Sen Gupta, D. D. Sarma, T. Mizokawa, A. Fujimori, M. Yuri, C.T. Chen, T. Fukumura, M. Kawasaki and H. Koinuma, J. Appl. Phys. 95, 3573 (2004).
  • Synthesis and Characterization of Mn doped ZnO Nanocrystals : Ranjani Viswanatha, Sameer Sapra, Subhra Sen Gupta, B. Satpati, P. V. Satyam, B. N. Dev and D. D. Sarma, J. Phys. Chem. B 108, 6303 (2004).

  • "Re-entrant Spectral Crossovers in Quantum Spin Chains : A Tale of Two Distinct Integrable Regimes Straddling A Quantum-Chaotic Phase", at the National Conference : “8th Indian Statistical Physics Community Meeting (ISPCM-2023)” held at TIFR-ICTS, Bangalore (February, 2023). [Presented by Ph.D. Student, Debojyoti Kundu].
  • "Variable-Range Spectral Correlations in 1D Correlated Quantum Spin-Chains", at the National conference on Quantum Condensed Matter (QMAT - 2021) organized by TIFR, Mumbai (Online mode, December, 2021). [Presented by Student, Debojyoti Kundu].
  • "Long-range Spectral Statistics in a Variety of Correlated Spin Models: A Comparison with Random Matrix Theory", at the 5th Young Investigators Meet on Quantum Condensed Matter Theory (YIMQCMT-2021) organized by NISER, Bhubaneshwar (Online mode, November, 2021). [Presented by Student, Debojyoti Kundu].
  • "RMT Spectral Distribution Crossovers in Random Spin Chains"  Oral Presentation at the APS March Meeting (Online Mode, March 2021).  [Presented by Student, Debojyoti Kundu].
  • "Short and Long-range Spectral Statistics in a Variety of Correlated Spin Models : A Comparison with Random Matrix Theory", at the 7th Indian Statistical Physics Community Meeting (ISPCM2020), held at ICTS, Bangalore (February 2020). [Presented by Student, Debojyoti Kundu].
  • "RMT Spectral Distribution Crossovers in Random Spin Systems", at the 6th Indian Statistical Physics Community Meeting (ISPCM2019), held at ICTS, Bangalore (February 2019). [Presented by Student, Debojyoti Kundu].
  • “Bond polarizability and large modification of the Hubbard U at the spin-state transition in Cobaltates” at the International Conference on Frontiers in Advanced Materials (FAM-2015), at the Indian Institute of Science, Bangalore, India. (June, 2015).
  • “Bond polarizability and large modification of the Hubbard U at the spin-state transition in Cobaltates” at the International Conference on Strongly Correlated Electron Systems (SCES-2014), at the Campus Saint Martin d’Hères, Grenoble, France. (July, 2014).
  • “Unusual role of Multipole Coulomb Interactions in determining Spin- orientation on Correlated Surfaces” at the Workshop on Oxide Electronics 20 (WOE20), at the National University of Singapore (NUS), Singapore. (September, 2013).
  • “The Importance of Inter-site Coherences in the X-ray Absorption Spectra of Mixed-valent Systems” at the MPI-UBC International School on Quantum Materials, held at the Max-Planck Institute for Solid State Research, Stuttgart, Germany. (October, 2010).
  • “High Momentum Transfer Shallow Core-to-valence Spectroscopy in the Actinides” at the APS March Meeting, held in Portland, Oregon, USA. (March, 2010)
  • “The Importance of High Momentum Transfer Shallow Core-to- valence Spectroscopy in the Actinides” at the PCAMM meeting, Simon Fraser University (SFU), Burnaby, Canada. (December, 2009).
  • “Non-resonant Inelastic X-ray Scattering (NIXS) in the Actinides and the Rare-earths: Some Generalities” at the Quantum Materials CIFAR Meeting, University of British Columbia (UBC), Vancouver, Canada. (May, 2009).
  • “Theoretical Investigation Of The Spin Reorientation Transition In Epitaxial Films Of NiO” at the International Conference on Magnetic Materials (ICMM), Saha Institute of Nuclear Physics (SINP), Kolkata, India. (December, 2007).
  • “Theory of the unusual doping and temperature dependent spectral weight transfer in the photoemission spectra of the manganites” at 1st Indo-Japan Conference, Indian Institute of Science (IISc), Bangalore, India. (February, 2006). 

  • Chaos and Wavefunction Multifractality in Disordered Quantum Spin Systems" at the National Conference : “8th Indian Statistical Physics Community Meeting (ISPCM-2023)” held at TIFR-ICTS, Bangalore (February, 2023).
  • “Chaos and Multifractality in Quantum Spin Systems" at the National Conference : “Young Investigator’s Meet on Quantum Condensed Matter Theory (YIMQCMT - 2022)” held at NISER, Bhubaneshwar (November, 2022).
  • “Symmetry, Integrability and Chaos in Quantum Spin Systems" at the National Conference : “d-d Transitions : A Discussion Meeting on the Electronic Structure of Materials” held at Colva, Goa (August, 2022).
  • "Universal Behaviour of Multi-point Spectral Correlations across Spectral Crossovers in Stochastic Quantum Spin Chains" at the International Conference : “5th Young Investigators Meet on Quantum Condensed Matter Theory (YIMQCMT-2021)" organized by NISER, Bhubaneshwar (November, 2021).
  • "Spectral Crossovers and Universality in Quantum Spin-chains Coupled to Random Fields",  at the International Conference : Interdisciplinary Topics in Advanced Materials (ITAM-2021) organized jointly by IISc and JNCASR, Bangalore. (July, 2021).
  • "Bond-polarizability induced Charge-Transfer to Mott-Hubbard Crossover at the Spin-state Transition in Cobaltates", at the 7th Indian Statistical Physics Community Meeting (ISPCM-2020) held at ICTS, Bangalore (February, 2020).
  • "A Quantum Mechanism of Magnetism in White Dwarfs", at the 6th Indian Statistical Physics Community Meeting (ISPCM-2019) held at ICTS, Bangalore (February, 2019).
  • "Magnetism in Super-Condensed Phases of Matter" at the Young Investigators Meet in Quantum Condensed Matter Theory (YIMQCMT-2018) held at S.N. Bose Centre, Kolkata (November, 2018).
  • “Strong Hybridization Effects on the "Hubbard U" and "Hund's Rule" in Strongly Correlated Electron Systems” at the CMPU, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India. (June, 2015). 
  • “Strong Hybridization Effects on the Hubbard U and the Hund’s coupling in Strongly Correlated Electron Systems” in the Department of Physics, University of Tokyo, Japan. (November, 2014).
  • “Unusual role of Multipole Coulomb Interactions in determining Spin-orientation on Correlated Surfaces” at the 6th Indo-Japan Meeting on Physics and Design of Multi-functional Correlated Materials, held at the University of Tokyo, Japan. (March, 2014).
  • “Breakdown of the single-site approximation in core-level X-ray spectroscopies” at the Saha Institute of Nuclear Physics (SINP), Kolkata, India. (December, 2012).
  • “An introduction to Non-resonant Inelastic X-ray Scattering (NIXS) - a versatile tool to study the electronic structure of complex oxides” at the Indo-EU ATHENA-2012 Advanced School on Modeling Complex Oxides, held at S. N. Bose National Centre for Basic Sciences. (April, 2012).
  • “Coexistence of bound and virtual-bound states in shallow-core to valence x-ray spectroscopies” at the S. N. Bose National Centre for Basic Sciences. (January, 2011).
  • “Non-resonant Inelastic X-ray Scattering (NIXS) in the Actinides and the Rare-earths: Some Generalities” at the X-ray Scattering Workshop at Stanford Institute of Materials and Energy Sciences Department, SLAC National Accelerator Laboratory, Stanford University, Palo Alto, USA. (August, 2009). 

Was selected for the ?Early Career Research Award? of DST-SERB, Project was activated in April 2018 (details given below) : Project Title : ?Theoretical Investigations of High Energy Optical Conductivity and Anomalous Spectral Weight Transfer in Cuprates and Other Strongly Correlated Electron Systems.? PI : Subhra Sen Gupta (Co-PI : None) Funding Agency : Science and Engineering Research Board (SERB) under the Department of Science and Technology (DST). Scheme : Early Career Research Award (ECRA) Scheme. Budget : INR 20,78,560 (About 21 Lakhs) Duration : 36 months (3 Yrs. : 2018 - 2021). Current Status : Successfully Completed, Formal Closure in Progress.