The Implications of Recent High Field Measurements on the Phase Diagram of Superconducting Uranium Ditelluride

Paramagnetic uranium ditelluride (UTe2) was recently identified as candidate for a spin-triplet superconductivity. The upper critical field exceeds the Pauli limit at every field orientation, with superconductivity persisting to a remarkable 10x the Pauli limit for H||b. Even more remarkably, in the field polarized state, a separate high field superconducting phase is found when field is offset about 30 degrees between b and c. Other evidence for a topologically non-trivial superconducting state include a point node gap structure, chiral surface modes that develop within the superconducting gap, and broken time reversal symmetry as indicated by the polar Kerr effect. Finally, I will describe recent high field electrical and magnetic measurements on superconducting UTe2, and discuss them in the context of other topologically nontrivial heavy fermion superconductors.