Thermal resistivity of layered 4He films on ZYX graphite below 2 K

Abstract

Thermal resistance and vapor pressure isotherms were taken near superfluid onset for ultrathin helium films adsorbed on a ZYX graphite wafer between 1-2 K and 3-7 atomic layers. Our data are consistent with previous graphite onsets and are compatible with a current model of film droplet formation. Overlap of thermal resistance curves at 1.19 and 139 K is believed to be associated with discrete layering effects of 2D superfluid film properties.

Onset of Superfluid Flow inHe4Films Adsorbed on Mylar

“…4. The values we obtain for b are similar to the value b = 5.5 obtained by oscillator techniques by Bishop and Reppy 3 for a helium film on Mylar at T = 1.2 K. They are substantially smaller than the values (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) found by Hess, Muirhead, and Dash 9 in recent studies of helium adsorbed on Au-plated Cu. Since b is not expected to be universal, the difference between the Mylar results and those for Au-plated Cu may not be significant.…”

Characterization of Pyrolytic Graphite Sheet: A New Type of Adsorption Substrate for Studies of Superfluid Thin Films

“…In addition, the substrate thickness should be as thin as possible not to shunt the temperature gradient by substrate itself when the film is in the normal state. The experiment by Polanco and Bretz [23] using a ZYX wafer of 25 × 25 × 5 mm 3 was successful to detect superfluid onset of the third layer of 4 He at T = 1.0 K. uPGS-10-µm should potentially be more advantageous for this experiment than ZYX because of its much better crystallinity [10].…”