Supersolid Helium and beating the diffraction limit

Two interesting pieces in Physics.

S Balibar writes about some new results in the study of supersolid phase transition in Helium:

Six years have passed since Kim and Chan [1,2] discovered supersolidity when they found that solid 4He does not rotate like a classical solid. Despite substantial effort, however, this phenomenon is not yet understood [3]. Some probably think that the research on this puzzling issue is too slow. Others, including myself, enjoy every new controversy and every new advance as if they were reading a detective story. In this tale, the latest twist is a study reported in Physical Review Letters by Oleksandr Syshchenko, James Day, and John Beamish at the University of Alberta, Canada [4], of the shear modulus of solid 4He in the temperature range where it becomes supersolid. They confirm that the observed change in stiffness is associated with a binding of dislocations to 3He impurities (Fig. 1) when the solid is cooled down (then unbinding when warming up, of course) and they show now that this binding is gradual because there is a rather wide distribution of binding energies. Why is this so important?

Blom and Widengren write about an optical microscope that beats the diffraction limit:

The classical view that lens-based optical microscopes cannot resolve details separated by less than half the wavelength of light is increasingly becoming a dated one. Several microscopy techniques, used either alone or in combination, can now beat the diffraction limit by at least a factor of 2. Now, in a paper appearing in Physical Review Letters, Claus Müller and Jörg Enderlein at Georg August University in Göttingen, Germany, add to this arsenal of techniques a method that essentially involves modifying an existing bench-top confocal-laser scanning microscope [1]. This type of microscope—called a CLSM for short—is already a fundamental tool for research, particularly in the biological sciences, and Müller and Enderlein’s proposal could influence a broad community.

Both the pieces are not only interesting but also written in a nice fashion; take a look!

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