Bulk and surface low-energy excitations in Y Ba 2 Cu 3 O 7 − δ studied by high-…
2007; American Physical Society; Volume: 75; Issue: 1 Linguagem: Inglês
10.1103/physrevb.75.014513
ISSN1550-235X
AutoresK. Nakayama, T. Sato, Kensei Terashima, H. Matsui, T. Takahashi, Masato Kubota, Kanta Ono, Terukazu Nishizaki, Yuki Takahashi, Norio Kobayashi,
Tópico(s)Iron-based superconductors research
ResumoWe have performed high-resolution angle-resolved photoemission spectroscopy on $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ (Y123; $\ensuremath{\delta}=0.06$; ${T}_{\mathrm{c}}=92\phantom{\rule{0.3em}{0ex}}\mathrm{K}$). By accurately determining the Fermi surface and energy band dispersion, we solve long-standing controversial issues as to the anomalous electronic states of Y-based high-${T}_{\mathrm{c}}$ cuprates. We unambiguously identified surface-bilayer-derived bonding and antibonding bands, together with their bulk counterparts. The surface bands are highly overdoped (hole concentration $x=0.29$), showing no evidence for the gap opening or the dispersion anomaly in the antinodal region, while the bulk bands show a clear ${d}_{{x}^{2}\text{\ensuremath{-}}{y}^{2}}$-wave superconducting gap and the Bogoliubov quasiparticlelike behavior with a characteristic energy scale of $50--60\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$ indicative of a strong electron-boson coupling in the superconducting state. All these results suggest that the metallic and superconducting states coexist at the adjacent bilayer of Y123 surface.
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