Interfaces in quantum systems

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Interfaces in quantum systems
Helsinki University of Technology
Low Temperature Laboratory

• Personnel of the Interface group
• Harry Alles
• Igor Todoshchenko
• Heikki Junes
• Matti Manninen

Collaboration Alexander Parshin Viktor Tsepelin
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Helium crystals
Picture from front cover of January 2005 issue of
Reviews of Modern Physics which contains ...

• The interest to the studies of helium crystals
  was lifted by the results of Kim and Chan (2004)
  Can a solid be superfluid? (the title of Moses
  Chans talk on ULTI meeting)
• Can one observe more than just three different
  types of facets on the surface of 4He crystals?
• Can one observe the magnetic crystallization
  waves on the interface between superfluid and
  solid 3He?

... the review The surface of helium crystals
by S. Balibar, H. Alles and A.Ya. Parshin (54
pages)
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Measurements on the melting curve of 4He
Our results Todoshchenko et al., Phys. Rev.
Lett. (2006) Todoshchenko et
al., JETP Lett. (2007)
Kim and Chan, Science (2004)
Melting pressure of ultra pure 4He (raw data
points)
Supersolid?
Solid
Normal liquid
Superfluid
p-p0, mbar
Our conclusion In the temperature range of 10
... 320 mK no sign of any thermodynamical phase
transition with single high-quality 4He crystals!
Deviation from the T4 -behavior due to phonons
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Search for new facets in 4He
Our Fabry-Pérot interferometer
Growing 3He crystal at T 0.55 mK, eleven
different types of facets were observed Tsepelin
et al., PRL(2001), Alles et al. (2001)
4He crystal at T 150 mK during very slow
growth where are the facets?
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Histogram method
In addition to the three observed types of facets
we have discovered five new types of facets on
the surface of hcp 4He crystals (details by Igor
Todoshchenko on the poster session)
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Future plan search for magnetic crystallization
waves in 3He

• In 3He, the crystallization waves are predicted
  to propagate on the superfluid-solid interface
  below a few tenths of mK (Andreev, 1995)
• Unlike in 4He, the crystallization waves in 3He
  will carry magnetic energy in addition to the
  usual kinetic energy in a high magnetic field
  the dispersion relation of the waves in 3He
  should become linear (instead of a 3/2 power law
  as in the case of 4He)
• It has not really been tried to observe the
  crystallization waves in 3He

Standing crystallization waves in 4He. Balibar,
Guthmann, and Rolley (1994).
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Experimental cell to be constructed

• Very simple cell of Lancaster-type which includes
  just two interdigital capacitors and a vibrating
  wire thermometer
• to cool the sample to the lowest possible
  temperature and try to excite the crystallization
  waves on the superfluid-solid interface of 3He at
  the frequency corresponding to one of the
  eigenmodes of the cell
• Our resolution should be of the order of a few mm
  (an order of magnitude better than with
  interferometric technique we have used)