New flow dissipation mechanisms in superfluid 3He

Superfluid helium quantum interference devices: physics and applications

We present an overview of recent developments related to superfluid helium quantum interference devices (SHeQUIDs). We discuss the physics of two reservoirs of superfluid helium coupled together and describe the quantum oscillations that result from varying the coupling strength. We explain the principles behind SHeQUIDs that can be built based on these oscillations and review some techniques and applications.

Dissipative currents in superfluid 3He weak links

We calculate the current-pressure relation for pinholes connecting two volumes of bulk superfluid 3He-B. The theory of multiple Andreev reflections, adapted from superconducting weak links, leads to a nonlinear dependence of the dc current on pressure bias. In arrays of pinholes one has to take into account oscillations of the texture at the Josephson frequency. The associated radiation of spin waves from the junction leads to an additional dissipative current at small biases, in agreement with measurements.

Supercurrent through hybrid junctions with anisotropic Cooper-pair condensates

A general formula for the supercurrent between different internal structures in a wide class of hybrid junctions is derived on the basis of the Andreev-reflection picture. The formula extends existing formulas and also enables us to analyze novel B-phase/A-phase/B-phase junctions in superfluid 3He systems. We propose a mechanism for pi states due to the (circumflex)l texture in the A phase of the junction, which could elucidate major features of the pi states with higher critical current ( H states) discovered in superfluid 3He weak links. The bistability of the pi states is also discussed.

Quantum interference of superfluid 3He

Celebrated interference experiments have demonstrated the wave nature of light and electrons, quantum interference being the manifestation of wave-particle duality. More recently, double-path interference experiments have also demonstrated the quantum-wave nature of beams of neutrons, atoms and Bose-Einstein condensates. In condensed matter systems, double-path quantum interference is observed in the d.c. superconducting quantum interference device (d.c. SQUID). Here we report a double-path quantum interference experiment involving a liquid: superfluid 3He. Using a geometry analogous to the superconducting d.c. SQUID, we control a quantum phase shift by using the rotation of the Earth, and find the classic interference pattern with periodicity determined by the 3He quantum of circulation.