报告题目：Theory of high temperature superconductivity of monolayer FeSe on the STO substrate and the transport theory of 2D superconductors

报 告 人：李定平，北京大学物理系

报告时间：2016年6月27日15:00

报告地点：理科楼C302

报告摘要：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.