Multiple superconducting phases and order-parameter evolution in pressurized UTe${}_2$

Abstract

The recently discovered heavy-fermion spin-triplet superconductor candidate UTe${}_2$ provides a rich platform for unconventional pairing and topological phenomena. However, limited has been known about its superconducting order parameters and their evolution with control parameters, largely due to the lack of appropriate symmetry-sensitive detections. Here, we report comprehensive point-contact spectroscopy measurements of pressurized UTe${}_2$ on the (0~0~1) surface. The observation of Andreev bound states strongly suggests the presence of a $p_z$ component in the superconducting order parameters. Quantitative analysis based on an extended Blonder-Tinkham-Klapwijk model unveils the superconducting order parameters with a finite odd-$k_z$ component (e.g. $B_{2u}$ or $B_{3u}$) for both ambient and pressurized UTe${}_2$. Remarkably, the multiple superconducting phases can be distinguished by a single parameter $⟨{\Delta }_z⟩/⟨{\Delta }_{x(y)}⟩$, the relative weight between the $p_z$-wave and $p_{x(y)}$-wave pairings. These findings place stringent constraints on the pairing symmetry and provide essential spectroscopic signatures for distinguishing pressure-induced multiple superconducting phases in UTe${}_2$.

24+17 pages, 5+14 figures, 1+1 tables