Thermal transport of helium-3 in a strongly confining channel

Abstract

In a neutral system such as liquid helium-3, transport of mass, heat, and spin provide information analogous to electrical counterparts in metals, superconductors and topological materials. Of particular interest is transport in strongly confining channels of height approaching the superfluid coherence length, where new quantum states are found and excitations bound to surfaces and edges should be present. Here we report on the thermal conduction of helium-3 in a 1.1 µm high microfabricated channel. In the normal state we observe a diffusive thermal conductivity that is approximately temperature independent, consistent with 1 recent work on the interference of bulk and boundary scattering. In the superfluid state we measure diffusive thermal transport in the absence of thermal counterflow. An anomalous thermal response is also detected in the superfluid which we suggest may arise from a flux of surface excitations.

Superfluid Optomechanics with Phononic Nanostructures

“…In the present work, we propose a novel architecture for superfluid optomechanics, based on engineered nanostructures allowing a better control over superfluid phonon propagation, preserving superfluid 4 He's exceptional intrinsic properties, and leading to enhanced quality factors and coupling strengths. Exploiting recent progress in quantum nanofluidics, concerning the confinement at the nanoscale of quantum fluids (liquid helium-4 [27][28][29][30][31][32][33][34] and liquid helium-3 [29,[35][36][37][38][39][40]), one can form a nanoscale cavity of typically hundreds of nm in height, and tens of µm in width defining the boundaries of a picogram or femtogram scale superfluid acoustic resonator [30][31][32]. Such superfluid acoustic resonator could be formed by means of a microsale hollow volume within a glass or silicon substrate.…”