Direct evidence for Cooper pairing without a spectral gap in a disordered superconductor above Tc

Koen M. Bastiaans, Damianos Chatzopoulos, Jian Feng Ge, Doohee Cho, Willem O. Tromp, Jan M. van Ruitenbeek, Mark H. Fischer, Pieter J. de Visser, David J. Thoen, Eduard F.C. Driessen, Teunis M. Klapwijk, Milan P. Allan

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


The idea that preformed Cooper pairs could exist in a superconductor at temperatures higher than its zero-resistance critical temperature (Tc) has been explored for unconventional, interfacial, and disordered superconductors, but direct experimental evidence is lacking. We used scanning tunneling noise spectroscopy to show that preformed Cooper pairs exist up to temperatures much higher than Tc in the disordered superconductor titanium nitride by observing an enhancement in the shot noise that is equivalent to a change of the effective charge from one to two electron charges. We further show that the spectroscopic gap fills up rather than closes with increasing temperature. Our results demonstrate the existence of a state above Tc that, much like an ordinary metal, has no (pseudo)gap but carries charge through paired electrons.

Original languageEnglish
Issue number6567
Publication statusPublished - 2021 Oct 29

Bibliographical note

Funding Information:
This work was supported by the European Research Council (ERC StG SpinMelt) and by the Netherlands Organization for Scientific Research (NWO/OCW) as part of the Frontiers of Nanoscience program, as well as through a Vidi grant (680-47-536). D.Cho. was supported by the National Research Foundation of Korea (NRF) funded by the Korea government (MSIT) (grants 2020R1C1C1007895 and 2017R1A5A1014862) and the Yonsei University Research Fund (grant 2019-22-0209). P.J.dV. was supported by the Netherlands Organization for Scientific Research NWO (Veni grant 639.041.750);

Publisher Copyright:
Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works

All Science Journal Classification (ASJC) codes

  • General


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