Interplay of Odd-parity Bulk Superconductivity with Superconducting Topological Surface State of UTe2

UTe₂ is emerging as a key candidate for nodal spin-triplet topological superconductivity. While its superconducting order parameter, Δ(k), has not been determined directly, recent advances have brought us closer to a definitive understanding. In odd-parity superconductors, a unique subgap quasiparticle surface band (QSB) is predicted for energies |E| ≤ Δ and, for typical Fermi surface geometries, the QSB is also a superconductive topological surface state. Quasiparticle interference (QPI) imaging is a promising technique for determining Δ(k) but here is occurring in a complex situation, especially because the (0-11) cleave surface is at an angle of 24 degrees to the crystal axis. In the normal state we observe distinct quasiparticle interference patterns on this (0-11) surface, characterized by a set of modulation vectors q_i which we demonstrated are dominated by two open Fermi surfaces. These phenomena dominate the odd-parity bulk Δ(k) interplay with QPI in the QSB of UTe₂.