Y. J. Yan

Electron-Doped Sr 2 IrO 4 : An Analogue of Hole-Doped Cuprate Superconductors Demonstrated by Scanning Tunneling Microscopy

Sr2IrO4 was predicted to be a high temperature superconductor upon electron doping since it highly resembles the cuprates in crystal structure, electronic structure and magnetic coupling constants. Here we report a scanning tunneling microscopy/spectroscopy (STM/STS) study of Sr2IrO4 with surface electron doping by depositing potassium (K) atoms. At the 0.5-0.7 monolayer (ML) K coverage, we observed a sharp, V-shaped gap with about 95% loss of density of state (DOS) at EFand visible coherence peaks. The gap magnitude is 25-30 meV for 0.5-0.6 ML K coverage and it closes around 50 K. These behaviors exhibit clear signature of superconductivity. Furthermore, we found that with increased electron doping, the system gradually evolves from an insulating state to a normal metallic state, via a pseudogap-like state and possible superconducting state. Our data suggest possible high temperature superconductivity in electron doped Sr2IrO4, and its remarkable analogy to the cuprates.

Surface electronic structure and isotropic superconducting gap in ( Li 0.8 Fe 0.2 ) OH Fe Se

Using angle-resolved photoemission spectroscopy (ARPES), we revealed the surface electronic structure and superconducting gap of (Li

Surface electronic structure and evidence of plain s -wave superconductivity in ( L i 0.8 F e 0.2 ) OHFeSe

_{0.8}

Superconductivity across Lifshitz transition and anomalous insulating state in surface K–dosed (Li0.8Fe0.2OH)FeSe

Fe

Possible Nodeless Superconducting Gaps in Bi

_{0.2}

_2

)OHFeSe, an intercalated FeSe-derived superconductor without antiferromagnetic phase or Fe-vacancy order in the FeSe layers, and with a superconducting transition temperature (

Sr

T_c

_2

)

CaCu

\sim

_2

40 K. We found that (Li