报告题目：Substrate effects of monolayer FeSe superconductor

报 告 人：Tao Jia，Stanford University

报告时间：2016年9月22日14：00

报告地点：理科楼C109

报告摘要：The enhancement of SrTiO3 (STO) substrate on the superconductivity of FeSe is dramatic [1]. Whereas bulk FeSe has a transisition temperature (Tc) of 8 K [2], the Tc of monolayer (1ML) FeSe on STO (001) is measured to be 40-100 K via various methods[1, 3-4]. Therefore the mechanism behind this Tc enhancement is of hugh interest in the field of superconducting heterostructures.

Here we show three experiments demonstrating the importance of interfacial electron-phonon coupling on the enhanced Tc of FeSe/STO. First, we observed replica bands in FeSe/STO (001) [4]. This indicates that there is strong electron-phonon coupling between monolayer FeSe and STO substrate, which may be pivotal for the Tc enhancement. Second, we observed polaron bands in STO (110) and monolayer FeSe/STO (110) [5]. This confirms the hypothesis of Zhou et al [6] that electron-phonon coupling is also essential in the FeSe/STO (110) system. Most conclusively, we grew highly strained 1ML FeSe on the rectangular (100) face of rutile TiO2, and observed the coexistence of replica bands and superconductivity with a Tc of 63 K [7]. From the similar Tc between this system and 1ML FeSe on STO, we conclude that strain and dielectric constant are likely unimportant to the enhanced Tc in these systems, and that interfacial coupling plays an essential role.

A systematic comparison of 1ML FeSe on TiO2 with other systems in the FeSe family can show that, while charge transfer alone can enhance Tc, it is only with the addition of interfacial electron-phonon coupling that Tc can be increased to the level seen in 1ML FeSe on STO.