Extreme magnetic field-boosted superconductivity

Applied magnetic fields underlie exotic quantum states, such as the fractional quantum Hall effect¹ and Bose-Einstein condensation of spin excitations². Superconductivity, however, is inherently antagonistic towards magnetic fields. Only in rare cases^3-5 can these effects be mitigated over limited fields, leading to re-entrant superconductivity. Here, we report the coexistence of multiple high-field re-entrant superconducting phases in the spin-triplet superconductor UTe₂ (ref. ⁶). We observe superconductivity in the highest magnetic field range identified for any re-entrant superconductor, beyond 65 T. Although the stability of superconductivity in these high magnetic fields challenges current theoretical models, these extreme properties seem to reflect a new kind of exotic superconductivity rooted in magnetic fluctuations⁷ and boosted by a quantum dimensional crossover⁸.