Topological Surface State Visualization in Spin-Triplet Superconductor UTe2

30 Nov 2023
Seminars and colloquia
Simpkins Lee
Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU

J.C. Séamus Davis, Oxford University

Although UTe2 appears to be the first 3D spin-triplet topological superconductor, its superconductive order-parameter has not yet been established. If spin-triplet, it should have odd parity so that  and, in addition, may break time-reversal symmetry. A distinctive identifier of  3D spin-triplet topological superconductors is the appearance of an Andreev bound state (ABS) on all surfaces parallel to a nodal axis, due to the presence of a topological surface band (TSB). Moreover, theory shows that specific ABS characteristics observable in tunneling to an s-wave superconductor distinguish between chiral and non-chiral . To search for such phenomena in UTe2 we employ s-wave superconductive scan-tip imaging of UTe2[1] to discover a powerful zero-energy ABS signature at the (0-11) crystal termination[2]. Its imaging yields quasiparticle scattering interference signatures of two  nodes aligned with the crystal a-axis. Most critically, development of the zero-energy Andreev conductance peak into two finite-energy particle-hole symmetric conductance maxima as the tunnel barrier is reduced, signifies that UTe2 superconductivity is non-chiral. Overall, the discovery of a TSB, of its a zero-energy ABS, of internodal scattering along the a-axis, and of splitting the zero-energy Andreev conductance maximum due to s-wave proximity, categorizes the superconductive as the odd-parity non-chiral B3u state[2].


[1] Nature, 618, 921–927 (2023) 

[3] Gu, Wang, et alScience (2023)