Phase Coherence and Andreev Reflection in Topological Insulator Devices


Topological insulators (TIs) have attracted immense interest because they host helical surface states. Protected by time-reversal symmetry, they are robust to nonmagnetic disorder. When superconductivity is induced in these helical states, they are predicted to emulate p-wave pairing symmetry, with Majorana states bound to vortices. Majorana bound states possess non-Abelian exchange statistics that can be probed through interferometry. Here, we take a significant step towards Majorana interferometry by observing pronounced Fabry-Pérot oscillations in a TI sandwiched between a superconducting and a normal lead. For energies below the superconducting gap, we observe a doubling in the frequency of the oscillations, arising from an additional phase from Andreev reflection. When a magnetic field is applied perpendicular to the TI surface, a number of very sharp and gate-tunable conductance peaks appear at or near zero energy, which has consequences for interpreting spectroscopic probes of Majorana fermions. Our results demonstrate that TIs are a promising platform for exploring phase-coherent transport in a solid-state system.



Keywords and Phrases

Condensed Matter Physics; Interferometry; Seismic Waves; Superconductivity; Andreev Reflection; Conductance Peaks; Phase-coherent Transport; Solid-state System; Spectroscopic Probes; Superconducting Gaps; Time Reversal Symmetries; Topological Insulators; Electric Insulators

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

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© 2014 American Physical Society (APS), All rights reserved.

Publication Date

01 Nov 2014

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