期刊
NANO LETTERS
卷 19, 期 8, 页码 4890-4896出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.9b00844
关键词
Higher order topology; 2D superconductor; hinge modes; Andreev reflection
类别
资金
- National Science Foundation [DMR-1709987]
- Office of Science, U.S. Department of Energy [DE-SC0012704]
- Elemental Strategy Initiative
- CREST, JST [JPMJCR15F3]
- Institute of Basic Science (IBS) in Korea
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 FeTe0.55Se0.45 (FTS) may also be topologically nontrivial. Should the superconducting order be s(+/-), 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 c-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.
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