Ions and atoms in superfluid helium (4He)

We review the previous conclusion [J.Y. Ryu, Y.C. Chung and S.D. Choi, Phys. Rev. B 32, 7769 (1984)] that the trace property Tr(ABC) = Tr(CAB) leads to two different cyclotron transition absorption formulae in the electron-phonon systems in the lowest order approximation. The pictorial expression and the calculated linewidths in Ge and Si show that the socalled EWC scheme is more seeming than the socalled MWC scheme. The difference is expected to disappear if we take into account all the higher order perturbation terms or start with the many body formalism in the complete scheme.     

Ions and atoms in superfluid helium (4He)

New experimental results for mobilities in superfluid helium of the alkali earth ions Be⁺, Mg⁺, Ca⁺, Sr⁺ and Ba⁺ in the temperature region from 1.27 up to 1.66 K are reported. Surprisingly, the temperature dependence of the Be⁺ ion mobility, measured here for the first time, is more similar to that of the He⁺ ion than to the heavier alkali earth ions. This behavior may suggest a snowball like structure for the defect around Be⁺ in contrast to the bubble like defects around the heavier alkali earth ions.     

Thermally driven josephson oscillations in superfluid 4He

We find that a temperature differential can drive superfluid oscillations in 4He. The oscillations are excited by a heater which causes a time dependent temperature differential across an array of 70 nm apertures. By measuring the oscillation frequency and simultaneously determining both temperature and pressure differentials we prove the validity of the most general form of the Josephson frequency relation. These observations were made near saturated vapor pressure, within a few mK of the superfluid transition temperature.     

Electrons on superfluid He

Low-frequency transport properties of the Wigner solid on normal and superfluid ³He have been studied. It is known that the Wigner solid deforms the free surface of liquid He to form a dimple lattice. The low-frequency resistivity is successfully interpreted by the ballistic and specular scattering of ³He quasiparticles from the dimple lattice. The resistivity decreases abruptly below the superfluid transition temperature. For superfluid ³He-A, the l-texture, presumably perpendicularly oriented to the free surface, has an essential influence on the resistivity.