## Theory of high temperature superconductivity of monolayer FeSe on the STO substrate and the transport theory of 2D superconductors

Speaker: 李定平 (北京大学物理系)

Time: June 27, 2016 15:00

Place: 理科楼C302

摘要**：**Part one: Pairing in one atomic layer thick two dimensional electron gas by a single at band of high energy longitudinal optical phonons is considered. The polar dielectric SrTiO3 (STO) exhibits such an energetic phonon mode and the 2DEG is created both when one unit cell FeSe layer is grown on its (100) surface and on the interface with another dielectric like LaAlO3 (LAO). We obtain a quantitative description of both systems by solving the gap equation for Tc for arbitrary Fermi energy, electron-phonon coupling and the phonon frequency, and direct (RPA) electron-electron repulsion strength. The high temperature superconductivity in 1UCFeSe/STO is possible due to a combination of three factors: high LO phonon frequency, large electron-phonon coupling and huge dielectric constant of the substrate suppression the Coulomb repulsion.

Part two: We use Ginzburg-Landau theory to study the transport of 2D superconductors. Based on improved Gaussian variational approximation, we calculate the transition temperature and superfluid density. Using time dependent Ginzburg Landau theory, we obtain the IV curve and magneto resistance. Then We compare the theoretical results with the experimental data.

**个人简介：**工作领域：高温超导理论，特别是二类超导体涡旋物态物理性质的研究；波色爱因斯坦凝聚理论；多体量子理论和场论方法的研究；量子霍尔效应。

科研成果：李定平教授近年来对高温超导体涡旋态和BEC相关领域进行了系统研究，已发表SCI收录论文数篇，其中包括Reviews of Modern Physics 1篇，Physical Review Letters 4篇, Physical Review B 14篇，Physical Review A 4篇, Nuclear Physics B 4篇， Physics Letters B 2篇。