Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

Feb. 8, 2024 at 2 p.m. in IPH Lorentzraum 05-127Prof. Dr. Peter van Loock

Institut für Physik

loock@uni-mainz.de

Dr. Lars von der Wense

Institut für Physik

lars.vonderwense@uni-mainz.de

Prof. J.C. Séamus Davis (University of Oxford, Oxford, UK)

Although UTe2 appears to be the first 3D spin-triplet topological superconductor, its superconductive order-parameter Δ_k has not yet been established. If spin-triplet, it should have odd parity so that Δ_(-k)=-Δ_k 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 Δ_k. 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 Δ_k 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 Δ_k as the odd-parity non-chiral B3u state [2], which is equivalent to the planar state of superfluid 3He.

[1] Nature 618, 921 (2023)

[3] Gu, Wang, et al. Science (2023)