Direct imaging of electron transfer and its influence on superconducting pairing at FeSe/SrTiO3 interface

Weiwei Zhao, Mingda Li, Cui Zu Chang, Jue Jiang, Lijun Wu, Chaoxing Liu, Jagadeesh S. Moodera, Yimei Zhu, Moses H.W. Chan

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

The exact mechanism responsible for the significant enhancement of the superconducting transition temperature (Tc) of monolayer iron selenide (FeSe) films on SrTiO3 (STO) over that of bulk FeSe is an open issue. We present the results of a coordinated study of electrical transport, low temperature electron energy-loss spectroscopy (EELS), and high-Angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) measurements on FeSe/STO films of different thicknesses. HAADF-STEM imaging together with EELS mapping across the FeSe/STO interface shows direct evidence of electrons transferred from STO to the FeSe layer. The transferred electrons were found to accumulate within the first two atomic layers of the FeSe films near the STO substrate. An additional Se layer is also resolved to reside between the FeSe film and the TiOx-terminated STO substrate. Our transport results found that a positive backgate applied from STO is particularly effective in enhancing Tc of the films while minimally changing the carrier density. This increase in Tc is due to the positive backgate that "pulls" the transferred electrons in FeSe films closer to the interface and thus enhances their coupling to interfacial phonons and also the electron-electron interaction within FeSe films.

Original languageEnglish (US)
Article numbereaao2682
JournalScience Advances
Volume4
Issue number3
DOIs
StatePublished - Mar 16 2018

All Science Journal Classification (ASJC) codes

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