Abstract
Topological insulators (TIs) have attracted immense interest because they host helical surface states. Protected by time-reversal symmetry, they are robust to non-magnetic 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 which can be probed through interferometry. Here, we take a significant step towards Majorana interferometry by observing pronounced Fabry-Perot oscillations in a TI sandwiched between a superconducting and normal lead. For energies below the superconducting gap, we observe a doubling in the frequency of the oscillations, arising from the additional phase accumulated 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.
Highlights
When electrons travel far distances without scattering off of impurities, their wavelike nature becomes apparent through signatures of interference
It has been pointed out that weak antilocalization in superconductor-semiconductor devices could survive in the presence of broken time-reversal symmetry, leading to low-energy anomalies that are nearly identical in appearance to those attributed to Majorana fermions [29]
We present transport measurements of the Topological insulators (TIs) Bi2Se3 in contact with both a superconducting lead and a normal metal lead
Summary
When electrons travel far distances without scattering off of impurities, their wavelike nature becomes apparent through signatures of interference. Constructive interference of reflected waves leads to periodic modulation of total transmission through the barrier, resulting in resonant transmission whenever the electron wavelength is an integer multiple of twice the barrier length. This is equivalent to kFL 1⁄4 πn, where kF is the Fermi wave vector, L is the barrier length, and n is a nonzero integer. Our results encourage further studies of gate-tunable phase coherence in Bi2Se3 in order to perform interferometric searches for MBSs. For example, it is necessary to discern what role topological surface states play in the Fabry-Pérot oscillations
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