Nishwal Gora

Research and Projects

Main Interests: Quantum Magnetism, Neutron Diffraction, Biological Physics, Bacterial Turbulence, Statistical Physics, Computational Physics, Modelling and Visualisation of Physical Systems, Polymer assembly, Chromatin Dynamics.

Overview

Publications

Magnetocalorics in Spin-Supersolid Candidate Na2BaCo(PO4)2

Zeeman split Kramers doublets publication image

T. I. Popescu, N. Gora, F. Demmel, Z. Xu, R. Zhong, T. J. Williams, R. J. Cava, G. Xu, and C. Stock

Physical Review Letters 134, 136703 (2025)

High-field neutron spectroscopy reveals coupled Zeeman-split Kramers doublets in the triangular antiferromagnet Na2BaCo(PO4)2. These drive ferromagnetic excitations that become overdamped near a quantum critical point, underpinning strong magnetocaloric effects and identifying Kramers doublet systems as promising low-temperature refrigerants.

DOI: https://doi.org/10.1103/PhysRevLett.134.136703

Magnetoelastic Honeycomb Fragmentation in VI3

VI3 honeycomb fragmentation publication image

E. Shen, T. I. Popescu, N. Gora, K. Guratinder, E. Chan, H. Lane, J. A. Rodriguez-Rivera, G. Xu, P. M. Gehring, R. A. Ewings, A. N. Fitch, and C. Stock

Physical Review B (Accepted, 2025)

We investigate magnetoelastic coupling in the two-dimensional van der Waals magnet VI3. Neutron and x-ray diffraction reveal a symmetry-breaking structural transition near TS ≈ 80 K, driven by orbital degeneracy, followed by ferromagnetic ordering near TC ≈ 50 K. Group-theoretical analysis indicates a transition from rhombohedral R3 to triclinic P1 or P1, producing two crystallographically inequivalent V3+ sites. Neutron spectroscopy shows dominant exchange only between symmetry-equivalent sites, fragmenting the honeycomb lattice into two interpenetrating magnetic sublattices.

DOI: https://doi.org/10.1103/pkc4-vyj8

Projects

Understanding Bond-Dependent Exchange in CoTiO3

CoTiO3 project image

This study applies a Green’s function response model to spin-wave excitations in CoTiO3, developing a novel mathematical framework incorporating a rotating frame and single-ion Co2+ physics; findings emphasize strong bond-dependent exchange interactions modeled via Resonating Valence Bond (RVB) theory, with dimer formation proposed as the source of anisotropy, validated by deriving θCW = 17.4 K and constraining exchange and molecular field terms to ~4.0 ± 0.2 meV, highlighting cobaltates like CoTiO3 as spin-liquid candidates.

Testing the Validity of Kepler’s Third Law

Kepler simulation project image

By simulating the Solar System with Newtonian dynamics and the Verlet method, this project determined an optimal time step of 0.5 days, keeping energy fluctuations to just 4.36×10⁻³%. Over 500 simulated years, the model accurately reproduced orbital periods, perihelia, and aphelia, and captured phenomena like Mercury’s apsidal precession. The results confirmed Kepler’s Third Law, even when planetary masses were altered, allowing exploration of how changes in planet sizes affect neighboring orbits.

Currently Working On

Modelling Bacterial Turbulence with Finite Tumbling

In this work, we investigate how introducing a finite tumbling duration into models of bacterial swimmers affects the onset of hydrodynamic instabilities, as revealed through changes in the system’s dispersion relations. We treat the population as consisting of runners and tumblers, with stochastic switching between the two states at prescribed rates. This leads to a coupled pair of Smoluchowski equations for the distribution functions of each population, incorporating both translational and rotational dynamics.

Unlike the instantaneous reorientation assumed in classic run-and-tumble models, tumblers here undergo active reorientation at a finite angular velocity, while also experiencing the same hydrodynamic couplings as runners. We identify the uniform, isotropic steady state of the system and perform a linear stability analysis about this base state. By projecting perturbations onto monopole, dipole, and quadrupole spherical harmonics, the governing equations reduce to a tractable eigenvalue problem.

This formulation allows us to quantify how finite tumbling modifies the critical parameters for instability onset, alters the growth rates of unstable modes, and changes the relative contributions of hydrodynamic and reorientation mechanisms. The results provide a systematic route to connect microscopic swimmer dynamics with emergent large-scale flow patterns in active suspensions.

Hopfield Network and Chromatin memory

This project explores whether the diverse conformational states emerging from chromatin folding—particularly those associated with transcription factory formation—can act as stable memory states in the cell’s regulatory landscape. Building on the connection between induced phase separation in chromatin and the emergence of transcriptional hubs, we investigate whether these folded states can serve as attractors in a Hopfield network framework. In this analogy, the Waddington landscape is reinterpreted as a network of memory basins, where cellular states are “remembered” and re-established following division. The aim is to bridge physical models of chromatin organization with neural network theory, providing insight into how genome architecture encodes and preserves cellular identity.