STM measurements of Ni impurity effects in Bi2212

29th International Symposium on Superconductivity

Nakagawa, A.^1 ; Sakaidani, T.^1 ; Kiguchi, Y.^1 ; Uto, T.^1 ; Matsuda, A.^1

Department of Physics, Schools of Advanced Science and Engineering, Waseda University, Okubo 3-4-1, Shinjuku, Tokyo

160-8555, Japan^1

关键词: Density of state;    Electronic systems;    Impurity effect;    Measured temperatures;    Measurements of;    Temperature dependence;    Temperature independents;    Temperature range;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/871/1/012012/pdf
DOI  :  10.1088/1742-6596/871/1/012012

来源: IOP

【 摘 要 】

We report on the STS measurements for the temperature dependences of density-of-states for optimally-doped and overdoped samples. In the tunnelling spectra above TCin an overdoped sample, we found two types of a pseudogap; the large one, which had a typical pseudogap size and decreased with increasing a temperature, and the small one, which seemed almost temperature independent in our measured temperature range. The large gap seemed to switch to the small one with some overlap region with increasing a temperature. Similar behaviour was found in the optimally doped samples with an enhanced gap size and the temperature range. We identified the large gap as a conventional pseudogap and the small one as a new pseudogap, which is associated with Ni impurity. This shows a peculiarity of Ni impurity, and suggests an unusual interaction between an impurity and the Cu-O electronic system.