利用扫描隧道显微术对SrTiO_(3)(001)上生长CoSe/FeSe异质界面结构和谱学研究

Study on the structural and electronic properties of CoSe/FeSe heterostructures grown on SrTiO_(3) using scanning tunneling microscopy

硒化铁/钛酸锶(001)(FeSe/SrTiO_(3)(001),FeSe/STO)中界面增强的超导电性一直是近些年凝聚态物理领域的热点问题之一,基于FeSe薄膜构筑异质界面是调控其超导电性和构筑新奇量子物态的重要手段。本文报道了利用分子束外延在SrTiO_(3)(001)衬底上制备了高质量硒化钴-硒化铁(CoSe/FeSe)纵向异质结的方法,利用扫描隧道显微镜和扫描隧道谱详细研究了该异质界面的电子性质和电子态密度的实空间分布。由于CoSe/FeSe界面存在强烈的电荷转移,FeSe处于过掺杂状态,导致FeSe/STO界面相互作用已不满足非绝热近似,以及FeSe中超导电性的消失。空间依赖的扫描隧道谱显示,CoSe/FeSe的异质界面边缘处出现了晶向依赖的边缘电子态和边角电子态,这些边界上的电子态受到CoSe/FeSe界面电荷转移效应的调制。该研究为基于单层FeSe/STO界面超导电性的调控及量子结构的构筑提供了借鉴。

The interface-enhanced superconductivity of FeSe/SrTiO_(3) has been one of the most attractive topics in the field of condensed matter physics.Fabricating heterostructures based on ultrathin FeSe films provides a promising method to tune their superconductivity and to construct novel quantum states.Here,we prepared high-quality CoSe/FeSe vertical heterostructure films on SrTiO_(3)(001)substrate by molecular beam epitaxy.Scanning tunneling microscopy(STM)and scanning tunneling spectroscopy(STS)were employed to investigate their electronic properties and the spatial distribution of electronic states.Due to the significant interfacial charge transfer from CoSe to FeSe,FeSe was in an over-doped state,which broken the non-adiabatic approximation in FeSe/STO and suppressed its superconductivity.The space-resolved STS measurements revealed the direction-dependent edge states and corner states tuned by the interfacial charge transfer at the CoSe/FeSe interface.This work provides a reference for the tuning of superconductivity and the construction of quantum structures based on single-layer FeSe/SrTiO_(3).