Isospin magnetism and spin-polarized superconductivity in Bernal bilayer graphene
Abstract
In conventional superconductors, Cooper pairing occurs between electrons of opposite spin. We observe spin-polarized superconductivity in Bernal bilayer graphene when doped to a saddle-point van Hove singularity generated by a large applied perpendicular electric field. We observe a cascade of electrostatic gate-tuned transitions between electronic phases distinguished by their polarization within the isospin space defined by the combination of the spin and momentum-space valley degrees of freedom. Although all of these phases are metallic at zero magnetic field, we observe a transition to a superconducting state at finite magnetic field B ‖ ≈ 150 milliteslas applied parallel to the two-dimensional sheet. Superconductivity occurs near a symmetry-breaking transition and exists exclusively above the B ‖ limit expected of a paramagnetic superconductor with the observed transition critical temperature T C ≈ 30 millikelvins, consistent with a spin-triplet order parameter.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Feb 18, 2022
- Source ID
- 10.1126/science.abm8386
Entities
People
- Andrea Young
- Caitlin L. Patterson
- Fangyuan Yang
- Haoxin Zhou
- Kenji Watanabe
- Liam A. Cohen
- Ludwig Holleis
- Takashi Taniguchi
- William Huynh
- Yu Saito
Organizations
- National Institute for Materials Science
- University of California, Santa Barbara