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SUMMARY:The third sound as an electric field generator
DTSTART;VALUE=DATE-TIME:20181205T104500Z
DTEND;VALUE=DATE-TIME:20181205T110500Z
DTSTAMP;VALUE=DATE-TIME:20260419T011441Z
UID:indico-contribution-10@indico.bitp.kiev.ua
DESCRIPTION:Speakers: Aleksandr Konstantinov (B.Verkin Institute for Low T
 emperature Physics and Engineering  of the National Academy of Sciences of
  Ukraine)\nIt is predicted that oscillations of temperature during propaga
 tion of third sound in a thin superfluid film cause appearance of an alter
 nating electric field in the surrounding space\, i.e. the third sound acts
  as a generator of the electric field [1].\nAs known\, the helium atoms ha
 ve no dipole\, quadrupole and other multipole moments. The situation chang
 es in the vicinity of the wall. Interaction of helium with the container w
 alls leads to the emergence of a nonzero average dipole moment of the heli
 um atoms directed along the normal to the wall. This leads to polarization
  of the film. Oscillations of its surface are accompanied by polarization 
 oscillations\, which cause the appearance of the electric fields over the 
 film. Specificity of a superfluid film is associated with the ability to c
 ause oscillations of the film surface by periodically heating the film bou
 ndary. As a result\, due to the anomalously large thermomechanical effect\
 , a small temperature difference $\\Delta T$ leads to large fluctuations i
 n film height and electrical potential $\\Delta \\varphi$. It turns out th
 at the differential thermal e.m.f. $\\Delta \\varphi/\\Delta T$  exceeds i
 ts value for typical metals. The predicted effect can be considered as an 
 electrical analogue of the fountain effect.\nUsing the method of I.E. Dzya
 loshinskii\, the average electric field over the system "atom-solid" was c
 alculated. It is shown that this electrical field is equivalent to the fie
 ld of the dipole moment of the atom (induced by substrate) and its image. 
 The polarization of the system\, associated with its inhomogeneity (analog
 ue of the flexoelectric effect)\, was also considered. It has been establi
 shed that the flexoelectric effect leads only to a small renormalization o
 f the dipole moment induced by the substrate. The equations describing the
  propagation of the third sound through the film have been solved. The eff
 ects of evaporation and condensation of helium atoms were taken into accou
 nt. The relationship between oscillating parts of the height and temperatu
 re of the film was found for the low-temperature and high-temperature regi
 ons. For helium film covering a hollow cylinder on the outside or inside\,
  an analytical expression for the electric field in space has been found. 
 The coefficient of proportionality between the electric potential and the 
 oscillating part of the film temperature (differential thermal e.m.f) was 
 calculated.\n[1] S. I. Shevchenko and A. M. Konstantinov\, J. Low Temp. Ph
 ys. (2018).\n\nhttps://indico.bitp.kiev.ua/event/2/contributions/10/
LOCATION:
URL:https://indico.bitp.kiev.ua/event/2/contributions/10/
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