Evidence for Suppressed Screening on the Surface of High Temperature La2-xSrxCuO4 and Nd2-xCexCuO4 Superconductors

Taguchi Munetaka

Chainani Ashish

Horiba Koji

Takata Yasutaka

Yabashi Makina

Tamasaku Kenji

Nishino Yoshinori

Miwa Daigo

Ishikawa Tetsuya

Takeuchi Tomoyuki

Yamamoto Kazuo

Matsunami Masaharu

Shin Shik

Yokoya Takayoshi

Ikenaga Eiji

Kobayashi Keisuke

Mochiku Takashi

Hirata Kazuto

Hori Junya

Ishii Kiyotaka

Nakamura Fumihiko

Suzuki Takashi

Physical Review Letters

Hard x-ray photoemission spectroscopy (PES) of Cu core electronic states, with a probing depth of ∼60, is used to show that the Zhang-Rice singlet feature is present in La2CuO4 but is absent in Nd2CuO4. Hole and electron doping in La2-xSrxCuO4 (LSCO) and Nd2-xCexCuO4 (NCCO) result in new well-screened features which are missing in soft x-ray PES. Impurity Anderson model calculations establish screening from doped states as its origin, which is strongly suppressed within 15 of the surface. Complemented with x-ray absorption spectroscopy, the small chemical-potential shift in core levels (∼0.2eV) are shown to be consistent with modifications of valence and conduction band states spanning the band gap (∼1eV) upon hole and electron doping in LSCO and NCCO.

eng

American Physical Society

Copyright (c) 2005 American Physical Society.

[ISSN] 0031-9007

[DOI] 10.1103/PhysRevLett.95.177002

[NCID] AA00773679

[DOI] http://dx.doi.org/10.1103/PhysRevB.62.4142