Collapse of Vapor-Filled Multielectron Bubbles Held Against a Surface
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Collapse of Vapor‑Filled Multielectron Bubbles Held Against a Surface P. K. Rath1 · Y. Huang2 · A. Ghosh1,2 Received: 14 September 2019 / Accepted: 14 January 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Multielectron bubbles (MEBs) are cavities in liquid helium containing a layer of electrons pinned to the inner surface of the bubbles. Previous experimental work carried out with MEBs in bulk helium-4 above the lambda point showed MEBs can contain vapor, which condenses in a time approximately proportional to the volume of the bubble, and this observation was further confirmed by numerical simulations. In the present work, we describe experiments where the MEBs are held against a solid substrate. We found the rate of vapor condensation and therefore the speed of collapse of the bubble to be orders of magnitude faster compared to MEBs in bulk. We discuss a numerical model and the associated difficulties to explain this difference. Keywords Multielectron bubbles · Liquid helium · Lifetime
1 Introduction Electrons on the surface of liquid 4He see a potential barrier of 1 eV [1] due to Pauli’s exclusion principle (arising due to completely filled shells of H e4 atoms) but experience a long-range attractive interaction through electrical polarization of the bulk liquid. As a result, electrons experience a confining potential with quantized energy states along the perpendicular direction from the liquid surface but remain free to move parallel to the surface forming a two-dimensional electron system (2DES) [2, 3]. When the electron density on the bulk helium surface or the applied electric field perpendicular to the charged helium surface crosses a critical value (~ 109 cm−2, and 4 kV/cm, respectively), the surface starts to become unstable (electrohydrodynamic instability, or EHD for short) and consequently breaks to form
* Y. Huang [email protected] 1
Department of Physics, Indian Institute of Science, Bangalore 560012, India
2
Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore 560012, India
13
Vol.:(0123456789)
Journal of Low Temperature Physics
bubbles of micron to millimeter sizes. These are referred as multielectron bubbles [4] or MEBs, which contain electrons floating on their inner surfaces, and provide a promising platform to test theories [5] of interacting electrons on curved surfaces. A number of experimental studies [6–11] have been carried out on MEBs, investigating their generation as well as their physical properties. They can be stably trapped in bulk liquid helium using a 2D Paul trap [12] using appropriate trapping parameters [13] which are quite different from parameters used in conventional ion traps. Depending on the method of generation, the MEBs can contain a significant amount of vapor. The rate of condensation of the vapor inside the MEBs is determined by the rate at which the liquid can carry out the latent heat, which is very fast for the liquid below the lambda point. On the other hand, at temperature
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