Majorana surface states in UTe₂ with quasi-2D Fermi surfaces

UTe₂ has attracted significant attention as it is widely recognized as a spin-triplet superconductor, with the potential to host Majorana fermions as excitations in a topological superconductor. Pairing symmetry plays a crucial role in realizing topological superconductivity, but it remains a subject of debate. The geometry of the Fermi surface is also essential for understanding the topological nature of superconductivity. However, recent dHvA experiments revealed quasi-2D Fermi surfaces of cylindrical shape, which suggests that UTe₂ may be topologically trivial as a 3D class DIII superconductor.

In this talk, we explore the possible realization of topological crystalline superconductivity in UTe₂ with quasi-2D Fermi surfaces [1]. We investigate Majorana surface states on all symmetric planes (100, 010, and 001 planes) for all symmetry-allowed odd-parity pairing states, and clarify the corresponding topological invariants characterized by crystalline symmetry. Furthermore, the 011 plane, an easily cleaved surface, hosts a nontrivial topological invariant for a 1D class DIII superconductor. Recent scanning tunneling microscopy and spectroscopy experiments on this plane have been conducted to probe the nature of the surface states [2]. We discuss the pairing symmetry and the presence of Majorana surface states by comparing our theoretical results with these experimental findings.



[1] J. Tei, et al., Phys. Rev. B 107, 144517 (2023).

[2] Q. Gu, et al., Nature 618, 921 (2023).