Unconventional order parameter induced by helical chiral molecules adsorbed on a metal proximity coupled to a superconductor

Tamar Shapira, Hen Alpern, Shira Yochelis, Ting Kuo Lee, Chao Cheng Kaun, Yossi Paltiel, Gad Koren, Oded Millo*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

Following our previous results, which provide evidence for the emergence of a chiral p-wave triplet-pairing component in superconducting Nb upon the adsorption of chiral molecules, we turned to investigate whether such an effect can take place in a proximal superconductor consisting of metal on superconductor bilayer. Note that in such proximity systems, correlated electron-hole (Andreev) pairs exist in the normal metal rather than genuine Cooper pairs. To that end, we used scanning tunneling spectroscopy (STS) on thin Au films grown in-situ on NbN (a conventional s-wave superconductor) before and after adsorbing helical chiral, alpha-helix polyalanine molecules. The tunneling spectra measured on the pristine Au surface showed conventional (s-wave like) proximity gaps. However, upon molecules adsorption the spectra significantly changed, all exhibiting a zero-bias conductance peak embedded inside a gap, indicating unconventional superconductivity. The peak reduced with magnetic field but did not split, consistent with equal-spin triplet-pairing p-wave symmetry. In contrast, adsorption of nonhelical chiral cysteine molecules did not yield any apparent change in the order parameter, and the tunneling spectra exhibited only gaps free of in-gap structure.

Original languageAmerican English
Article number214513
JournalPhysical Review B
Volume98
Issue number21
DOIs
StatePublished - 20 Dec 2018

Bibliographical note

Publisher Copyright:
© 2018 American Physical Society.

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