Visualizing the Odd-parity Superconducting Order Parameter and its Quasiparticle Surface Band in UTe2
H. H. Wills Physics Laboratory, University of Bristol（布里斯托大学）；Clarendon Laboratory, University of Oxford（牛津大学）；Department of Physics, University College Cork（科克大学）
Shuqiu Wang, J. C. Séamus Davis
备注：
27 pages, 6 figures
发表信息：
Journal of Low Temperature Physics, 222, 57 (2026)
A distinctive identifier of nodal intrinsic topological superconductivity (ITS) would the appearance of an Andreev bound state on crystal surfaces parallel to the nodal axis, in the form of a topological quasiparticle surface band (QSB) appearing only for $T < T_C$. Moreover, theory shows that specific QSB characteristics observable in tunneling to an s-wave superconductor can distinguish between chiral and non-chiral ITS order parameter $Δ_k$. To search for such phenomena in $\text{UTe}_2$, s-wave superconductive scan-tip scanning tunneling microscopy (STM) imaging was employed. It reveals an intense zero-energy Andreev conductance maximum at the $\text{UTe}_2$ (0-11) crystal termination. Development of the zero-energy Andreev conductance peak into two finite-energy particle-hole symmetric conductance maxima as the tunnel barrier is reduced, then signifies that $\text{UTe}_2$ superconductivity is non-chiral. Quasiparticle interference imaging (QPI) for an ITS material should be dominated by the QSB for energies within the superconductive energy gap $|E| \le Δ$, so that bulk $Δ(k)$ characteristics of the ITS can only be detected excursively. Again using a superconducting scan-tip, the in-gap quasiparticle interference patterns of the QSB of $\text{UTe}_2$ were visualized. Specifically, a band of Bogoliubov quasiparticles appears as a characteristic sextet $q_i$ :$i = 1-6$ of interference wavevectors showing that QSB dispersions $k(E)$ occur only for energies $|E| \le Δ_{max}$ and only within the range of Fermi momenta projected onto the (0-11) crystal surface. In combination, these phenomena are consistent with a bulk $Δ(k)$ exhibiting spin triplet, time-reversal conserving, odd-parity, a-axis nodal, $B_{3u}$ symmetry in $\text{UTe}_2$.
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Harvard University（哈佛大学）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所）；University of Maryland, College Park（马里兰大学帕克分校）；National Institute of Standards and Technology（美国国家标准与技术研究院）；Washington University in St. Louis（圣路易斯华盛顿大学）；Canadian Institute for Advanced Research（加拿大高级研究院）
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