Mechanism of field-reentrant superconductivity in UTe2 above 400 kG
In plain words
In UTe2, superconductivity reappears in magnetic fields of about 400 to 650 kG when the field is tilted at a particular angle, fields far above those that destroy ordinary superconductors.
Precise statement
In UTe2 with the field tilted from the b axis toward c by roughly 20 to 40 degrees, superconductivity reappears above the metamagnetic transition $H_m \sim 350\,\mathrm{kG}$ and survives to $\sim 650\,\mathrm{kG}$ (Ran et al., Nature Physics 2019). Determine the pairing mechanism and order parameter of this field-polarized phase: triplet pairing mediated by field-enhanced ferromagnetic fluctuations, compensation of the exchange field by the applied field (Jaccarino-Peter mechanism), or pairing on a Fermi surface reconstructed at $H_m$. An answer predicts the angular window and the upper critical field from a model with independently measured parameters.
What would settle it
Fermi-surface and magnetization measurements across $H_m$ combined with a calculation that reproduces the angular window and upper field of the reentrant phase.
Status in the literature
Unverified note
Helm et al. (Nature Communications 2024) proposed field-induced compensation of magnetic exchange; no mechanism is agreed.