arXiv subjects

Hirakjyoti Sarma

Publications and source records attributed to Hirakjyoti Sarma.

4 recordsLinked to original sources

arXiv2026

Effect of confinement anisotropy on particle transport and structural relaxation of finite dust clusters in complex plasma

A finite dusty plasma cluster of charged microparticles confined in an anisotropic potential well is investigated experimentally and through Langevin dynamics simulations. As the confinement anisotropy is increased, the cluster undergoes a structural transition from near isotropic concentric shells to a linear chain configuration. The spatiotemporal modes of the cluster are analyzed by using Singular Value Decomposition. At weaker confinement anisotropies, two modes are dominant. Mode 1, corresponding to a breathing-type oscillation of the cluster, and mode 2, representing an azimuthal rotational motion of the cluster, together carry around 99$\%$ of the signal energy. With increasing anisotropy, the dominance of mode 2 decreases and that of mode 1 increases. This mode restructuring is accompanied by an increasingly non-Gaussian particle displacement statistics as evidenced by positive values of the Non-Gaussian Parameter maintained over an extended time duration. Simultaneously, the increasing dominance of mode 1 and suppression of mode 2 is accompanied by a significant slowing down of structural relaxation, with the cluster eventually exhibiting signatures of structural arrest. At weaker anisotropy, the experimentally measured dynamical quantities are very sensitive to the initial conditions which account for the discrepancy between the experiment and initial condition averaged simulation results for these observables. This study offers insight into the mechanisms underlying anomalous transport and structural relaxation in anisotropically confined many-body systems.

physics.plasm-ph↗

arXiv2026

Anisotropy-induced Inhomogeneous Melting in Finite Dust Clusters

We present the first experimental evidence of inhomogeneous melting in a finite dusty plasma crystal confined in an anisotropic potential well. By systematically tuning the confinement anisotropy and applying controlled laser heating, distinct melting patterns are observed. Spectral-mode analysis based on Singular Value Decomposition of particle trajectories reveals that increasing laser power redistributes energy into specific collective modes, triggering localized structural destabilization. Molecular Dynamics simulations reproduce the observations and show that confinement-controlled mode coupling with laser heating governs the melting dynamics. These results establish geometric anisotropy as a key control parameter for inhomogeneous melting in finite coupled systems.

physics.plasm-ph↗

arXiv2025

Structure and dynamics of finite three-dimensional Yukawa clusters in complex plasmas : Newtonian versus Langevin Dynamics

The structure and dynamics of a harmonically confined three dimensional finite dust cluster are investigated via both Langevin Dynamics (LD) and frictionless Molecular Dynamics (fMD) simulation. The static structure of the system is analyzed through the Radial Distribution Function, Center-two-particle correlation function(C2P) and angular correlation function. The intra-shell angular correlation, Radial Distribution Function and C2P remains largely unaffected by the dynamics employed. However, the inter-shell angular correlation exhibits sharp peaks at irregular angular intervals in fMD which are not seen in LD indicating strongly correlated motion of the two spherical shells in the cluster in fMD. The single particle dynamics of the cluster is characterized by the Van - Hove self autocorrelation function and Mean Squared Displacement (MSD). Notably, the Van - Hove autocorrelation function in fMD simulations exhibits narrower width and higher peak height as compared to the LD simulations, suggesting greater particle mobility in LD. Trajectory analysis reveals a rotational motion of the particles about a common axis in fMD which disappears with progressively increasing friction coefficient. We show that the disappearance of rotational motion with the introduction of neutral friction in the dynamics is due to the much faster relaxation of the interparticle distance as well as interparticle angular separation in LD as compared to fMD.

physics.plasm-ph↗

arXiv2023

Phase transition of three-dimensional finite-sized charged dust clusters in a plasma environment

The dynamics of a harmonically trapped three-dimensional Yukawa ball of charged dust particles immersed in plasma is investigated as function of external magnetic field and Coulomb coupling parameter using molecular dynamics simulation. It is shown that the harmonically trapped dust particles organize themselves into nested spherical shells. The particles start rotating in a coherent order as the magnetic field reaches a critical value corresponding to the coupling parameter of the system of dust particles. The magnetically controlled charged dust cluster of finite size undergoes a first-order phase transition from disordered to ordered phase. At sufficiently high coupling and strong magnetic field, the vibrational mode of this finite-sized charged dust cluster freezes, and the system retains only rotational motion.

physics.plasm-ph↗