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.
A. D. Finck et al., "Phase Coherence and Andreev Reflection in Topological Insulator Devices," Physical Review X, vol. 4, no. 4, American Physical Society (APS), Nov 2014.
The definitive version is available at https://doi.org/10.1103/PhysRevX.4.041022
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)
Article - Journal
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01 Nov 2014