Superfluid Phases and Vortex Dynamics in Helium-3

Superfluid Helium-3 serves as a paradigm for unconventional quantum fluids, exhibiting multiple p-wave paired phases distinguished by broken symmetries and topological order. In bulk, the chiral A-phase and the time-reversal-symmetric B-phase emerge under varying pressure and temperature conditions, while reduced dimensionality or anisotropic confinement gives rise to the polar phase and its distortions. The order parameter in each phase encodes the spin and orbital pairing structure, with vortices and other topological defects reflecting the underlying homotopy of the order-parameter manifold. Vortex dynamics in these phases—ranging from integer-quantum vortices to half-quantum vortices—offer insights into macroscopic quantum phenomena, while surface or boundary bound states, such as Andreev-bound states, mediate dissipation and transport. Research on Helium-3 superfluidity not only illuminates fundamental questions in low-temperature physics but also provides analogues for cosmological defect formation and potential platforms for topologically protected quantum technologies.

Research from Nature Portfolio

Recent studies have demonstrated control over phase symmetry in superfluid Helium-3 confined within anisotropic silica aerogel, revealing a temperature-driven orbital-flop transition between chiral A-phase and time-reversal-symmetric B-phase. The orientation of the orbital quantization axis is fixed by strain direction in the aerogel, and diffusion-limited cluster aggregation modelling combined with small-angle X-ray analysis attributes this flop to competing short- and long-range structural motifs. Another advance shows that the B-phase surface bound states form an independent two-dimensional superfluid at boundaries, with quasiparticle currents flowing diffusively within the quantum well surrounding the bulk. This work establishes that surface Andreev-bound states can be harnessed to engineer two-dimensional condensates with tunable topology, offering new platforms for probing low-dimensional superfluid dynamics.

Superfluid Phases and Vortex Dynamics in Helium-3 publication trend

The graph below shows the total number of articles in superfluid phases and vortex dynamics in helium-3 across all publications each year (not limited to Nature Index journals).

Technical terms

Superfluid phase: A state of matter in which the fluid flows without viscosity, exhibiting macroscopic quantum coherence.

Cooper pairing: The pairing of two fermions with opposite momenta and spins, leading to a condensate and superfluidity.

A-phase / B-phase: Distinct superfluid phases of Helium-3; the A-phase is chiral with anisotropic pairing, while the B-phase is isotropic and time-reversal symmetric.

Anisotropic aerogel: A porous, strain-imposed medium with direction-dependent structure used to confine and manipulate superfluid Helium-3.

Order parameter: A complex field describing the amplitude and symmetry of the superfluid condensate.

Half-quantum vortex (HQV): A topological defect carrying half the circulation quantum, often coupling spin and orbital degrees of freedom.

Andreev-bound state: A quasiparticle state localised at surfaces or vortex cores due to suppression of the superfluid energy gap.

References

1. Orbital-flop transition of superfluid 3He in anisotropic silica aerogel. Nature Communications (2024).
2. Transport of bound quasiparticle states in a two-dimensional boundary superfluid. Nature Communications (2023).
3. String monopoles, string walls, vortex skyrmions, and nexus objects in the polar distorted B phase of He3. Physical Review Research (2020).
4. Vortices in Polar and β Phases of 3He. JETP Letters (2022).