Superfluid ${}^3$He-B Surface States in a Confined Geometry Probed by a Microelectromechanical Oscillator

Abstract

A microelectromechanical oscillator with a 0.73 $\mu$m gap structure is employed to probe the surface Andreev bound states in superfluid ${}^3$He-B. The surface specularity of the oscillator is increased by preplating it with 1.6 monolayers of ${}^4$He. In the linear regime, the temperature dependence of the damping coefficient is measured at various pressures, and the normalized energy gap is extracted. The damping coefficient increases after preplating at lower pressures, which is attributed to the decreased energy minigap of the surface bound states. The device is also driven into the nonlinear regime, where the temperature independent critical velocity at each pressure is measured. The critical velocity is observed to increase after preplating at all pressures, which might be related to the increased average energy gap. The observed behavior warrants a microscopic theory beyond a single parameter characterization of the surface.

10 pages, 15 figures, to be submitted to Physical Review B

References in corpus (6)

• Thermodynamic properties of thin films of superfluid 3He-A
• Crystalline order in superfluid 3He films
• Surface Majorana Cone of the Superfluid ${}^3$He B Phase
• Surface Specific Heat of ${}^3$He and Andreev Bound States
• Superfluid nanomechanical resonator for quantum nanofluidics
• Critical Velocity in the Presence of Surface Bound States in Superfluid ${}^3$He-B