Recent photoemission results of cuprate and transition metal dichalcogenide superconductors

 

Donglai Feng (Fudan University, Shanghai)

 

In this talk, I will present our recent studies of the electronic structure of cuprate superconductor Bi2Sr1.6La0.4CuO6+x (Bi2201), and the newly discovered superconductor 1T-CuxTiSe2.

In an optimally doped high quality Bi2201 superconductor, we unambiguously observed the symbolic superconducting coherence peak in the antinodal region, which has been widely observed in multi-CuO2-layer cuprate superconductors before. The associated peak-dip separation is just about 19 meV, which is much smaller than its counterparts in multi-layered compounds, but correlates with the energy scales of spin excitations in single layer cuprates.

In the new charge-density-wave system and superconductor 1T-CuxTiSe2, a correlated semiconductor band structure is revealed for the undoped case, which resolves a long-standing controversy in the system. The excitonic mechanism of the charge density wave, which was originally proposed by Kohn in the 1960's, is realized in this system. With Cu doping, the charge density wave is suppressed by the raising of the chemical potential, while the superconductivity is enhanced by the enhancement of the density of states, and possibly suppressed at higher doping by the strong scattering.