QFS2016 Book of Abstracts

Abstracts

P2.5 An energy gap in the spectrum of atomic excitations 4 He system.

Superfluidity. A.I. Karasevskii

Institute for Metal Physics, 36 Vernadsky boulevard, Kiev 03142, Ukraine The procedure of the reduction of the N-particle wave function, describing the collective motion of the atoms in the quantum system of He4, to the binary wave function of neighboring atoms is proposed. Considering the helium atoms as quantum particles, we calculated their energy in the ground and first excited state.It is shown that state of atoms in the liquid He4 is characterized by the discrete energy spectrum resulting in formation of s- and p- zones corresponding to the ground and excited states of helium atoms, separated by energy gap of value ≈ 5-8 K. The existence of a gap in the energy spectrum of the atomic excitation in He4 system allows us to draw an analogy between the physical mechanisms of superfluidity and classical superconductivity. P2.6 Observation of splitting and coalescence an with Multi electron bubbles Vadakkumbatt Vaisakh(1), Ghosh Ambarish(1,2). 1) Indian Institute of science, Department of physics, Bangalore, India, 560012. 2) Indian Institute of Science, Centre for Nano Science and Engineering, Bangalore, India, 560012. When the two dimensional layer of electrons above the surface of liquid helium is taken beyond a critical density, multielectron bubbles (MEBs) are formed. These are spherical cavities in liquid helium which contain electrons bound within a nanometre distance from their inner surfaces. MEBs form a model system for probing properties of interacting electrons over curved surfaces, but have been subject to limited experimental investigation. The purpose of this paper is to report on new surprising observations with MEBs, particularly related to their splitting and coalescence. In the presence of a high electric field, MEBs could be split into many smaller bubbles, where the electrons were distributed unequally between the daughter bubbles. Coalescence of MEBs could also be observed, in spite of the bubbles being negatively charged. The coalescence could be seen in the bulk liquid, as well as when the MEBs were attached to a solid surface. Analysis of these experimental results reveals a new way of tuning the density of electrons in MEBs, which will be essential to observe new electronic phases in this novel system.

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