Nontrivial Boundary-Mediated Superconducting Transport in a TRSB Topological Iron-Based Superconductor

Wenyao Liu; Gabriel Natale; Camron Farhang; Michael Geiwitz; Qishuo Tan; Xingyao Guo; Mason Gray; Vincent LambertiJazzmin Victorin; Huairuo Zhang; James L. Hart; Vsevolod Belosevich; Xi Ling; Qiong Ma; Wan Kyu Park; Kenji Watanabe; Takashi Taniguchi; Judy J. Cha; Albert V. Davydov; Kin Chung Fong; Ethan Arnault; Genda Gu; Rui-Xing Zhang; Enrico Rossi; Jing Xia; Kenneth S. Burch

arXiv · 2606.21507

Nontrivial Boundary-Mediated Superconducting Transport in a TRSB Topological Iron-Based Superconductor

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Abstract

The interplay of superconductivity, band topology, and spontaneous time-reversal-symmetry breaking (TRSB) is expected to enable topological superconducting boundary states. FeTe0.55Se0.45 provides a promising single-material platform because it combines superconductivity, nontrivial band topology, and spontaneous magnetization in the superconducting state. Here we report evidence for a boundary-mediated superconducting transport response in exfoliated Fe(Te,Se) devices. Polar Kerr measurements show that TRSB emerges below TKerr < Tc and coexists with superconductivity across multiple compositions, providing an independent symmetry-breaking scale for transport. Using crystallographically sharp, continuous edges and side-surface-dominant contacts, we find that topological FeTe0.55Se0.45 exhibits an anomalous conductance plateau absent in topologically trivial FeTe0.40Se0.60 and Fe1.02Te0.55Se0.45 under comparable measurements. This plateau requires uninterrupted sharp edges connecting source and drain, persists over micrometer-scale separations far exceeding the bulk coherence length, shows strongly suppressed thermal broadening, and collapses when the drain is moved to the top surface. Its temperature evolution follows the TRSB scale: the plateau remains weakly broadened below T*Kerr and disappears near TKerr rather than Tc. These doping-selective, edge-geometry-dependent, TRSB-correlated, and long-range nonlocal signatures establish experimental criteria for identifying boundary-mediated superconducting transport in FeTe0.55Se0.45 and motivate phase-sensitive and theoretical studies of its microscopic origin.

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Wenyao Liu, Gabriel Natale, Camron Farhang, Michael Geiwitz, Qishuo Tan, Xingyao Guo, Mason Gray, Vincent LambertiJazzmin Victorin, Huairuo Zhang, James L. Hart, Vsevolod Belosevich, Xi Ling, Qiong Ma, Wan Kyu Park, Kenji Watanabe, Takashi Taniguchi, Judy J. Cha, Albert V. Davydov, Kin Chung Fong, Ethan Arnault, Genda Gu, Rui-Xing Zhang, Enrico Rossi, Jing Xia, Kenneth S. Burch. 2026-06-19. Nontrivial Boundary-Mediated Superconducting Transport in a TRSB Topological Iron-Based Superconductor. https://arxiv.org/abs/2606.21507

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