Ultracold Quantum Gases & Supersolidity
Ground-state properties, quantum phase transitions, collective excitations and supersolid order in spin-orbit-coupled, coherently coupled and dipolar Bose–Einstein condensates.
ISF Postdoctoral Fellow
Theoretical physics of interacting quantum matter
I study emergent phenomena in ultracold quantum gases and correlated bosonic systems, with particular interests in supersolidity , nonequilibrium dynamics , collective excitations and quantum chaos .
I am currently an ISF Postdoctoral Fellow in the Department of Physics at Ben-Gurion University of the Negev , working with Prof. Doron Cohen. My work combines analytical many-body theory, semiclassical methods and large-scale numerical simulations to connect microscopic models with experimentally accessible observables.
Be'er Sheva, Israel
Ben-Gurion University
Quantum many-body theory
Current research
Correlated bosons, metastability and quantum chaos
Bose–Hubbard rings and chains · spectrum tomography · semiclassical–quantum correspondence
Research
Research directions
My research spans equilibrium and nonequilibrium many-body physics, with emphasis on systems in which competing interactions, symmetry breaking and correlations generate experimentally observable emergent behaviour.
Nonequilibrium & Finite-Temperature Dynamics
Universal coarsening and defect dynamics after quenches; stochastic classical-field methods (SGPE/SPGPE) for real-time thermal dynamics; and Hartree–Fock–Bogoliubov–Popov theory for spinor condensates.
Correlated Lattice Bosons & Quantum Chaos
Metastability, spectrum tomography and mixed regular–chaotic dynamics in Bose–Hubbard rings and chains, including the breakdown of mean-field descriptions in finite lattice systems.
Quantum Fluids of Light & Polaron Physics
Nonequilibrium dynamics and superfluidity in exciton–polariton condensates, together with impurity physics in Bose–Einstein condensates and driven–dissipative systems.
Selected results
Research highlights
Nonequilibrium universality
Universal coarsening dynamics
Showed that magnetic domains in a quenched quasi-2D spin-1 spin-orbit-coupled condensate grow as L(t) ∼ t0.66, placing these gases in the inertial-hydrodynamic binary-fluid universality class.
Finite-temperature quantum matter
Temperature control of supersolid order
Found that rising temperature can stabilise and enlarge the supersolid stripe phase rather than simply melt it, providing a counter-intuitive route to shifting phase boundaries through thermal fluctuations.
Spectroscopy
Collective-mode diagnostics
Computed low-lying dipole, breathing and spin-dipole excitations to identify phase boundaries through mode softening and roton-like instabilities, providing experimentally accessible signatures of quantum phases.
Many-body quantum chaos
Metastability & spectrum tomography
Combined many-body exact diagonalisation with semiclassical spectrum tomography to connect metastable currents with mixed regular–chaotic dynamics in Bose–Hubbard rings and chains.
Publications
Peer-reviewed articles
peer-reviewed articles, newest first.
Manuscripts in preparation
Rajat, Ritu and Sandeep Gautam, Universal coarsening dynamics of the supersolid stripe phase of spin-orbit-coupled spinor Bose–Einstein condensates .
Sunilkumar V, Rajat, Sandeep Gautam and Arko Roy, Thermodynamics of trapped coherently coupled Bose gases .
Recognition
Awards & distinctions
2026
Seal of Excellence — European Commission
Awarded to the Marie Skłodowska-Curie Postdoctoral Fellowship proposal SuperSQF – Supersolidity in Quantum Fluids , scored 92.6/100 .
March 2025
Best Oral Presentation Award
PHYCON 2025 · IIT Ropar, India
Methods
Theoretical & computational toolkit
Many-body theory
Quantum many-body theory; mean-field and Bogoliubov–de Gennes theory; Hartree–Fock–Bogoliubov–Popov theory; nonequilibrium scaling, universality and semiclassical phase-space methods.
Numerical methods
SGPE/SPGPE methods, finite-difference and pseudospectral solvers, basis expansion, Lanczos exact diagonalisation, large eigenvalue problems and real-time nonlinear evolution.
Programming
Fortran
Python
Mathematica
MATLAB
Bash
HPC & scientific libraries
LAPACK
ARPACK
BLAS
FFTW
OpenMP
OpenACC / GPU
Slurm
Scientific communication
Conference presentations
Oral presentations
Collective excitations and universal coarsening dynamics of a spin-orbit-coupled spin-1 Bose–Einstein condensate
PHYCON 2025 · IIT Ropar, India · March 2025
Best Oral Presentation Award
Temperature-induced supersolidity in spin-orbit-coupled Bose gases
QMAT 2024 · IIT Guwahati, India · December 2024
Temperature-induced supersolidity in spin-orbit-coupled Bose gases
Physics Day · IIT Ropar, India · March 2024
Poster presentations
Metastability, chaos and spectrum tomography for Bose–Hubbard rings and chains
Atomtronics 2026 · Centro de Ciencias de Benasque Pedro Pascual · Benasque, Spain · May–June 2026
Temperature-induced supersolidity in spin-orbit-coupled Bose gases
International Conference on BEC · SNBNCBS, Kolkata · November 2024
Temperature-induced supersolidity in spin-orbit-coupled Bose gases
Ultracold Atoms Japan 2024 · OIST, Japan · April 2024
Collective excitations in cigar-shaped spin-orbit-coupled spin-1 BECs
Quantum Technologies with Ultracold Atoms · IISER Pune · November 2023
Academic path
Experience & education
Oct 2025 – Present
ISF Postdoctoral Fellow
Ben-Gurion University of the Negev · Be'er Sheva, Israel
Strongly correlated lattice bosons: metastability, quantum chaos and phase transitions in Bose–Hubbard rings and chains, with Prof. Doron Cohen.
Jun 2025 – Oct 2025
Visiting Researcher
Indian Institute of Technology Ropar · India
Collective excitations and finite-temperature dynamics in coupled ultracold gases.
Dec 2019 – Jun 2025
PhD in Physics
Indian Institute of Technology Ropar · India
Thesis: Collective excitations and coarsening dynamics of spin-orbit-coupled spinor condensates. Advisor: Dr. Sandeep Gautam. Degree awarded 16 July 2025.
Jun 2019 – Jan 2022
Junior Research Fellow
Indian Institute of Technology Ropar · India