Evidence for Helical Hinge Zero Modes in an Fe-Based Superconductor.
basic_science · Level V
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- Record sourced from PubMed, PMID 31268723.
- Also identified by DOI 10.1021/acs.nanolett.9b00844.
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Abstract
Combining topology and superconductivity provides a powerful tool for investigating fundamental physics as well as a route to fault-tolerant quantum computing. There is mounting evidence that the Fe-based superconductor FeTe<sub>0.55</sub>Se<sub>0.45</sub> (FTS) may also be topologically nontrivial. Should the superconducting order be s<sup>±</sup>, then FTS could be a higher order topological superconductor with helical hinge zero modes (HHZMs). To test the presence of these modes, we have fabricated normal-metal/superconductor junctions on different surfaces via 2D atomic crystal heterostructures. As expected, junctions in contact with the hinge reveal a sharp zero bias anomaly that is absent when tunneling purely into the <i>c</i>-axis. Additionally, the shape and suppression with temperature are consistent with highly coherent modes along the hinge and are incongruous with other origins of zero bias anomalies. Additional measurements with soft-point contacts in bulk samples with various Fe interstitial contents demonstrate the intrinsic nature of the observed mode. Thus, we provide evidence that FTS is indeed a higher order topological superconductor.