Ultrasound conned many-electron bubbles in liquid helium

Indian physicists have proposed a new method of generation of multielectron bubbles in liquid helium with the help of ultrasound. It is possible to increase the charge density in the bubble and watching the bubble, even after the condensation of gaseous helium. The new method will be used to study the effects of surface curvature and quantum interactions in two-dimensional electron system. Article published in the journal Physical Review B.

On the surface of liquid helium in electron impact two forces: Coulomb repulsion due to the Pauli principle and the attraction due to the polarization of the liquid. Because of this above the surface of liquid helium occurs a two-dimensional electron system. At sufficiently high electron density on the surface can be transformed in a multielectron bubble — the cavity in fluid that contains many electrons. Multielectron bubbles will help to investigate the interaction of electrons on curved surfaces and allow to achieve electron concentration more than 2×1013 per square meter with such large concentrations of manifest quantum effects such as quantum melting.

To suppress the instability to achieve a high concentration of electrons, scientists use a charged thin film of liquid helium. This approach is limited to surface defects of the substrate and loss of electrons, moving along the quantum vortices, but the scientists turned to bring the electron concentration is 10 to15 per square meter. However, to date there has been no experimental observation of the quantum melting of two-dimensional electron system, although this would clarify the behavior of electrons in a two-dimensional system.

A group of Indian physicists led by Ambarisha Ghosh (Ambarish Ghosh) from the Indian Institute of Sciences proposed to create the instability of the charged surface of liquid helium with the help of ultrasound focused near a charged surface. For surface charging, the researchers used the foil from beta-radioactive Nickel-63. To monitor the behavior of liquid helium, the authors removed all on a high speed camera with a frame rate of 10,000 frames per second.

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