学术报告（11月20日）

主持人：姚道新教授

欢迎广大师生参加！

报告摘要：

This talk will cover our recent studies in three topics in condensed physics.  First, the propagation of tightly bound excitons and other local excitations will be discussed, using a newly developed theoretical / computational framework that treats the exciton as a composite boson rather than a particle-hole pair.  Its kinetic kernel then encapsulates the information of exciton propagation and decay, and allows several orders of lower computational expense. Second, the glide-translational symmetry of the Fe-based superconductors will be discussed, including its consequence in the electronic structure and in the superconducting pairing symmetry.  We will discuss an approximate approach using local gauge transformation.  The Cooper pairs are then shown to contains three components, explaining the puzzling experimental observation of superconducting gap anisotropy, and establishing the appearance of finite-momentum, odd-parity singlet, eta-pairing. Finally, the talk will cover a simple geometrical argument for the formation of superconducting dome in the phase diagram using the strong binding description of superconductivity.  This robust argument establishes for the first time strong quantum phase fluctuation at the overdoped regime, and form the foundation for the recent observation of weak doping dependent superconducting gap in the cuprates.

[1] Chi-Cheng Lee, et al., “First-principles method of propagation of tightly bound excitons in LiF: Verifying the exciton band structure with inelastic x-ray scattering”, Phys. Rev. Lett. 111, 157401 (2013).

[2] Chia-Hui Lin, et al, “One-Fe versus Two-Fe Brillouin Zone of Fe-Based Superconductors: Creation of the Electron Pockets via Translational Symmetry Breaking”, Phys. Rev. Lett. 107. 257001 (2011). 

[3] Chia-Hui Lin et al., “Orbital-Parity Distinct Superconducting Pairing Structures of Fe-based Superconductors under Glide Symmetry”, arXiv:1403.3687.

[4] “Kinetics-Driven Superconducting Gap in Underdoped Cuprate Superconductors Within the Strong-Coupling Limit” Y. Yildirim and Wei Ku, Phys. Rev. X 1, 011011 (2011).

报告人简介： 

顾威现为美国Brookhaven National Laborator & Stony Brook University教授。1991年获得台湾淡江大学学士学位。2000年获得美国田纳西大学（Knoxville）博士学位。2001-2003年在美国University of California Davis做博士后研究。2003年至今在美国Brookhaven National Laborator & Stony Brook University工作。主要研究领域为：关联电子材料的第一性原理原理计算，高温超导体的电子结构和物性，半导体，纳米结构，光电性质等。