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Studying the influence of a capping layer on interfacial superconductivity in FeSe/SrTiO3 heterostructures

What Has Been Achieved: we carried out a careful study of the effect of 3 different capping layers on interfacial superconductivity in FeSe/SrTiO3 heterostructures.

Importance of the Achievement: FeSe/SrTiO3 heterostructures shows superconductivity with relatively elevated critical temperatures. However, the fundamental understanding of this phenomenon is still quite incomplete. Furthermore, to use such materials for applications, we need to understand how best to preserve the high temperature superconductivity obtained in vacuo when a sample is under ambient conditions. This requires finding the optimal capping layer. Our study showed that the charge transfer from the capping layer plays a key role in this context. We also used optimally capped samples to search for possible signatures of exotic pairing by measuring the angle-dependent critical field and did not find any unusual anisotropy that could be attributed to exotic physics. This in house research study has also allowed us to establish the protocols for synthesizing a material that is of interest to users and has allowed to develop the in vacuo Nanoprobe electrical measurement capability as a powerful tool for users who wish to study 2D films without exposing them to ambient conditions.

Unique Feature(s) of the MIP that Enabled this Achievement: 2DCC-MIP’s multimodule MBE and surface characterization was critical for synthesizing high quality FeSe ilms and for measuring their superconducting behavior in the in vacuo pristine state.

(If Applicable) Publication:  Yanan Li, Ziqiao Wang, Run Xiao, Qi Li, Ke Wang, Anthony Richardella, Jian Wang, and Nitin Samarth, “Capping layer influence and isotropic in-plane upper critical field of the superconductivity at the FeSe/SrTiO3 interface,” Phys. Rev. Materials 5, 034802 (2021).  This research was carried out using the Penn State Two-Dimensional Crystal Consortium-Materials Innovation Platform (2DCC-MIP) under NSF Grant No. DMR-1539916. YL acknowledges support from the University of Chicago. AR and NS acknowledge support from NSF Grant No. DMR-1539916. RX acknowledges support from the Institute for Quantum Matter under DOE EFRC grant DE-SC0019331. QL acknowledges support from DOE under grant No. DE-FG02-08ER46531. JW acknowledges support from National Natural Science Foundation of China (No. 11888101).

Yanan Li, Ziqiao Wang, Run Xiao, Qi Li, Anthony Richardella, Nitin Samarth (Penn State) Jian Wang (Peking University)
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