LIST OF RESEARCHERS
Dr. Jaewon Choi (active), Dr. Oleksiy Zadorozhko (12-16)

TWO-DIMENSIONAL SUPERFLUID

Helium adsorbed on graphite provides an excellent realization of a number of nearly two-dimensional (2D) phenomena. The helium film grows layer by layer as the density of the ascorbate increases. The interaction potential between the helium atoms and graphite is much stronger than the He–He interaction. Due to this potential the first layer of helium on graphite is solid. The phase diagram of first layer is well known and has the variety of phases. Experiments revealed behavior corresponding to 2D gas, 2D liquid, commensurate and incommensurate phases.


TORSIONAL OSCILLATOR STUDY ON 2D SUPERFLUID

The phase diagram of second layer is not so clear. The interaction potential between the helium atoms and graphite is weaker comparing to the first layer, but the second layer remains solid. Experiments revealed that there is the drop of period of torsional oscillator at some densities of 2nd layer of solid helium film. It can be explained as an existence of zero point vacancy at commensurate phase or a superfluid. Main point in the studying helium adsorbed on graphite is the quality of substrate. For example, the surface homogeneities in Grafoil (size of crystallite ≈ 200A) substrates induces the broadening of the heat capacity near the density of the 3*3. At the same time the heat capacity of helium films adsorbed on the ZYX (size of crystallite ≈ 1800A) substrate shows the much sharper transition. Therefore, in order to solve the problem of unusual drop of period of torsional oscillator in 2nd layer of helium film we use torsional oscillators with graphite substrates of different quality.

  - Researcher: Dr. Oleisiy Zadorozhko
 

 

 

 

 

VIBRATION-FREE MEASUREMENT LABORATORY
The vibration-free measurement laboratory of KAIST Center for Supersolid and Quantum Matter Research (CSQR) was designed and constructed for high-precision TO experiments. The external mechanical vibration noise is cut off by three-level anti-vibration system. Currently three wet dilution refrigerators (base temperature ~15mK) made by Oxford Instruments are operated. To counter the recent helium shortage issue, Cryomech helium recovery system with two liquid helium plants (LHeP18) was installed and has operated without any serious problems since 2012.

MAILING ADDRESS 
CSQR Vibration-free Lab, Natural Science Building (E6), Department of Physics
Korea Advanced Institute of Science and Technology

373-1 Guseong-dong, Yuseong-gu, Daejeon, Republic of Korea 305701
(Phone) +82-42-350-8193

 
   
           

Helium Recovery System with two Liquid Helium Plants (LHeP18)

 

Newest Oxford Dilution Fridger

 
 
 

 

SUPERSOLID AND SOLID HELIUM
2D SUPERFLUID HELIUM
2D SUPERCONDUCTORS
TRANSPORT IN GRAPHENE
POLYMER PHYSICS