Non-Majorana origin of the half-integer conductance quantization elucidated by multiterminal superconductor–quantum anomalous Hall insulator heterostructure

Abstract

Chiral one-dimensional transport can be realized in thin films of a surface-insulating ferromagnetic topological insulator called quantum anomalous Hall insulator (QAHI). When superconducting (SC) pairing correlations are induced in the surface of such a material by putting an s-wave superconductor on the top, the resulting topological superconductivity gives rise to chiral Majorana edge modes. A quantized two-terminal conductance of 12(e2/h) was proposed as a smoking-gun evidence for the topological SC phase associated with a single chiral Majorana edge mode. There have been experiments to address this proposal, but the conclusion remains unclear. Here we formulate the edge transport in a multiterminal superconductor–QAHI heterostructure using the Landauer-Büttiker formalism. Compared to the original proposal for the 12(e2/h) quantization based on a simple two-terminal model, our formalism allows for deeper understanding of the origin of the quantization. The analysis of our experiments on multiterminal devices unambiguously shows that the half-integer conductance quantization arises from the equilibration of the potentials of the incoming edge states at the SC electrode, and hence it is not of Majorana origin.

Source-reported materials — not catalogue approval

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