报告时间：2015年6月27日上午10:00

报告地点：物理学院新楼5-112

报告人：王达 南京大学

简介：Electron-phonon coupling plays an important role not only in conventional BCS superconductors, but also in high temperature superconductors in which electronic correlation is mostly studied. How electron-phonon coupling interacts with electronic correlation is a long-standing problem and is still not clear now. With the help of functional renormalization group, we investigate their competition in a prototype Hubbard-Holstein model. At half-filling, we found spin-density-wave and charge-density-wave phases and the transition between them, while no superconducting phase arises. Upon finite doping, d-wave/s-wave superconductivity emerges in proximity to spin-density-wave/charge-density-wave phases. Counter-intuitively, we observe that lower-frequency Holstein-phonons are either less destructive, or even beneficial, to the various phases, resulting in a negative isotope effect.

邀请人：王宇副教授