Speaker: Prof. Chun-Liang Lin, Department of Electrophysics, National Yang Ming Chiao Tung University 
Time：2021/11/30  Tuesday 1:30PM-3:00PM
Place：Lecture room 124, Dept. of Phys. 
Title : Superconductivity in Plumbene-Based Superstructure
Abstract: 
Superconductivity in ultrathin film rises an issue to reconsider the pair correlation in BCS theory in two-dimensional (2D) limit. Former studies by using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) have observed the superconductivity in atomic-thickness layers of Pb and In on Si substrates [1, 2]. Besides, the current discovery of superconductivity in twist bilayer graphene drives the focus on electronic correlations in honeycomb lattices [3]. As an element of the carbon family, lead (Pb) has also been proposed a similar structure as graphene, which is called plumbene. Considering that plumbene is the heaviest element in graphene-like materials, it is expected to show the most significant spin-orbit coupling (SOC) effect. Theoretical predictions indicate that the tuning buckling and spin-orbit couplings in 2D honeycomb lattices may enhance the superconducting critical temperature [4, 5]. Accordingly, it is intriguing to investigate whether superconductivity exists in other plumbene-based superstructures. 
In the current study, a plumbene-based superstructure grown by deposition a small amount of Au on Pb(111) surface are found. By STM and temperature-dependent STS, a higher critical temperature (Tc) in plumbene-based superstructure than that of Pb substrate is observed, which is totally beyond the proximity effect. It strongly suggests that change of the Fermi surface induced by buckling and spin-orbit interaction modifies the density of states that enhances Tc in ultrathin plumbene-based superstructure.