Nariko Hosomi

Slippage of 4He Films Adsorbed on Grafoil

We applied the quartz-crystal microbalance (QCM) technique to 4He films adsorbed on grafoil. It was found that both of nonsuperfluid 4He films and the inert layers underneath the superfluid film slip under a certain condition at low temperatures, and that the temperature at which these films start to slip depends on the 4He areal density. In addition, this slippage also depended strongly on the amplitude of the quartz crystal.

Competition between the superfluidity and the slippage of 4He films adsorbed on porous gold

We have carried out QCM measurements for 4He films adsorbed on porous gold in the crossover region between the superfluidity and slippage. In relative low areal densities, the resonance frequency increases gradually below TS due to the slippage of solid film, while the superfluid onset is observed in high areal densities. In the crossover region, we observed a peuliar behavior: The inrease in the resonance frequency below TS is suddenly suppressed at a certain temperatue TD. From these observations, it is oncluded that the superfluidity and the slippage of 4He competes with eah other.

QCM studies of 4He films adsorbed on grafoil

Abstract We applied the quartz-crystal microbalance technique to a graphite substrate, and measured the slippage of nonsuperfluid 4 He films at MHz-frequency range, as well as the superfluidity. It was found that nonsuperfluid 4 He films undergo slipping at low temperatures, and that this slippage depends strongly on 4 He areal density.

Development of a combined atomic force microscope with an AT-cut quartz resonator

To study the microscopic mechanism of energy dissipation due to sliding motion, we are developing a combined atomic force microscope (AFM) with a quartz crystal microbalance (QCM) resonator. In this system, the loading force is controlled by AFM, while the energy dissipation is measured by the change in Q value of the quartz crystal. At room temperature, we have checked the energy dissipation for several substrates as a function of loading force. The energy dissipation depends both on substrate material and on oscillation amplitude.

Effect of 3He on superfluid 4He films adsorbed on Grafoil

We have studied an effect of 3He on superfluid 4He films adsorbed on exfoliated graphite (Grafoil) using a quartz-crystal microbalance (QCM) technique. It is known that zero-temperature superfluid mass and superfluid onset temperature of 4He films adsorbed on porous gold substrate are suppressed, or even eliminated with the addition of 3He. We found that the superfluid onset temperature of 4He films on graphite decreases with the addition of 3He. However, the superfluid mass does not increase monotonically with decreasing temperature; it has a peak and is suppressed below a certain temperature, which suggests a phase separation of the film at low temperatures.

Interfacial Friction of 4He Films Adsorbed on Grafoil Preplated with Kr

We report results for interfacial friction of nonsuperfluid 4He films adsorbed on Grafoil (exfoliated graphite) preplated with one atomic layer of Kr (4He/Kr/Gr). In the present experiment, the quartz‐crystal microbalance (QCM) technique was adopted, and the friction was measured down to 0.5 K for several oscillating amplitudes, ranging from 0.1 to 1 nm at 5 MHz. Above about the first layer completion, a decrease in the friction was clearly observed for a large amplitude below a certain temperature TS. This decrease occurs abruptly at around the second layer completion. Although 4He/Kr/Gr has a lower TS than 4He adsorbed on bare Grafoil when 4He is two atoms thick, the areal density dependence of TS is similar for the two systems.