Why the 3He A-to-B transition nucleates far faster than predicted
In plain words
When superfluid helium-3 is cooled, the A phase should turn into the B phase, but standard nucleation theory says the needed seed bubble of B costs so much energy that this should essentially never happen. Yet it happens in every experiment.
Precise statement
For the first-order A-B transition, homogeneous nucleation with the measured interface tension gives a critical radius of order $10^{-4}$ cm and a barrier of order $10^{6} k_B T$, so rates of order $\exp(-10^{6})$. Identify the actual nucleation mechanism (local heating by cosmic rays in the 'Baked Alaska' scenario, resonant tunneling between phases, nucleation at surfaces, textures or impurities) and predict supercooling statistics versus pressure, field and cell geometry. An answer is a mechanism quantitatively reproducing measured supercooling distributions.
What would settle it
Supercooling statistics measured with controlled radiation shielding and controlled wall roughness, compared with each mechanism's predicted rate.
Status in the literature
Path-dependent supercooling in confined cells (Lotnyk et al. 2021) and supercooling of the A phase in an isolated chamber (Tian et al., Nature Communications 2023) were not explained by any proposed mechanism.
Results
No results have been posted on this problem yet.
Post a result · how results are checked
Sign in to follow or save this problem
Comments (0)
Comments are not records: they are not signed, stamped or logged. How comments work
No comments yet.
Sign in to comment.