What is it about?

Clusters formed by a small number of particles are prevalent in various physical systems, such as those formed by ions in electromagnetic traps and electrons in quantum dots. These finite clusters often exhibit interesting properties that distinguish them from bulk homogeneous systems. In this work, we conducted a simulation study to understand the collective and single-particle dynamical behavior of finite harmonically confined 2D clusters in the presence of an external magnetic field. Our findings demonstrate that the interplay among different timescales within such systems leads to significant changes in collective phonon modes and self-diffusion of the particles within the cluster. At lower values of dust neutral collision frequency, an increase in magnetic field strength causes the phonon spectra of the finite 2D cluster to split into two distinct branches with the higher frequency branch approaching cyclotron frequency. But at a sufficiently larger value of dust neutral collision frequency, the distinct phonon spectra vanishes.

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Why is it important?

We observe that by tuning the external magnetic field strength, the cluster can transit from a normal to a super-diffusive regime. Understanding diffusion in confined geometries is crucial, as it arises in various biological systems. For instance, the movement of tracer particles within the crowded environment of living cells exhibits anomalous behavior in length and timescales below a few micrometers and several seconds (Rep. Prog. Phys. 76, 046602 (2013)). This study may therefore contribute to our understanding of diffusion in confined geometries. The single particle and collective phenomena presented in this paper can be observed in complex plasma experiments by adjusting the magnetic field strength such that the cyclotron time period becomes comparable to harmonic time period and dust-dust interaction time period, respectively.

Perspectives

The work presented in the paper was performed using an in-house developed Molecular Dynamics code. Writing the code was an enjoyable experience for me. Furthermore, studying confined Yukawa systems in both 2D and 3D settings entails rich physics, and I am delighted to explore this system through numerical simulation and analytical theories.

Hirakjyoti Sarma
Tezpur University

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This page is a summary of: Phonon spectra of finite dust clusters under a transverse external magnetic field, Physics of Plasmas, June 2024, American Institute of Physics,
DOI: 10.1063/5.0205947.
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