We report directional point-contact spectroscopy data on the novel Bi2Te3/Fe1+yTe interfacial superconductor for a Bi2Te3 thickness of 9 quintuple layers, bonded by van der Waals epitaxy to a Fe1+yTe film at an atomically sharp interface. Our data show a very large superconducting twin-gap structure with an energy scale exceeding that of bulk FeSe or FeSe1-xTex by a factor of 4. While the larger gap is isotropic and attributed to a thin FeTe layer in proximity of the interface, the smaller gap has a pronounced anisotropy and is associated with proximity-induced superconductivity in the topological insulator Bi2Te3. Zero resistance is lost above 8 K, but superconducting fluctuations are visible up to at least 12 K and the large gap is replaced by a pseudogap that persists up to 40 K. The spectra show a pronounced zero-bias conductance peak in the superconducting state, which may be a signature of an unconventional pairing mechanism.
@article{arxiv.1407.5875,
title = {Large gap, a pseudogap and proximity effect in the Bi2Te3/Fe1+yTe interfacial superconductor},
author = {M. Q. He and Q. L. He and J. Y. Shen and H. C. Liu and Y. Zheng and C. H. Wong and Q. H. Chen and J. N. Wang and K. T. Law and I. K. Sou and A. P. Petrovic and R. Lortz},
journal= {arXiv preprint arXiv:1407.5875},
year = {2014}
}