In this issue: Brownian Boomerangs, Tying Knots with Light, Ion Pair Simulates Quantum Phase Transitions
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Brownian Boomerangs
Boomerang-shaped particles in a fluid can transform random kicks from the surrounding molecules into motion in a particular direction.
Brownian motion – the erratic walk of small particles in a fluid due to the jostling of surrounding molecules – underpins many fundamental processes in nature. So far, experiments have only been able to observe it for particles with a simple shape (spherical or football-shaped). A US research team has now studied the Brownian motion for more complex geometries. The researchers used photolithography to make little polymer boomerangs and used a fast camera to watch their movements in a liquid. The videos showed that, over short times, the random jostling does not lead to a random direction of movement: the particles move preferentially in the direction of the line bisecting the angle of the boomerang arms. The finding may help understand the diffusion of complex biomolecules and lead to the design of nanoswimmers with tailored swimming patterns.
* Ayan Chakrabarty, Qi-Huo Wei (contact author) et al, “Brownian motion of boomerang colloidal particles”, Physical Review Letters (expected publication date: Oct 18)
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Tying Knots with Light
A team of researchers from the US, Poland and Spain has found a new class of solutions of Maxwell equations – the set of equations describing all electromagnetic phenomena - that contains all possible knots and links of a toroidal configuration. Should these knots be recreated with laser beams or magnetic fields, they might offer new ways to trap cold atoms or confine plasmas.
* Hridesh Kedia (contact author), I Bialynicki-Birula, D Peralta-Salas, WTM Irvine, “Tying knots in light fields”, Physical Review Letters (expected publication date: Oct 10)
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Ion Pair Simulates Quantum Phase Transitions
Properly prepared ensembles of ultracold atoms or ions can be used as “quantum simulators”, allowing researchers to recreate and study complex phenomena observed in solid-state systems. A new experiment performed at the Osaka University in Japan uses trapped ions to simulate polaritons - hybrid excitations that result from the combination of electromagnetic and mechanical waves. The researchers were able to use the scheme to realize a model for a superfluid-to-insulator phase transition that is common in condensed-matter physics.
* Kenji Toyoda (contact author) et al, “Experimental realization of a quantum phase transition of polaritonic excitations”, Physical Review Letters (expected publication date: Oct 14)
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Journal articles and preprints are available to journalists on request.
Matteo Rini, PhD
Deputy Editor, Physics
