Mingqiang Ren

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.

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

(\mathrm{L}{\mathrm{i}}_{0.8}\mathrm{F}{\mathrm{e}}_{0.2})\mathrm{OHFeSe}

Possible Nodeless Superconducting Gaps in Bi

is a newly discovered intercalated iron-selenide superconductor with a

_2

{T}_{c}

Sr

above 40 K, which is much higher than the

_2

{T}_{c}

CaCu

of bulk FeSe (8 K). Here we report a systematic study of

_2

(\mathrm{L}{\mathrm{i}}_{0.8}\mathrm{F}{\mathrm{e}}_{0.2})\mathrm{OHFeSe}

O

by low temperature scanning tunneling microscopy (STM). We observed two kinds of surface terminations, namely FeSe and