QFS2016 Book of Abstracts

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