Laser-excited ultrahigh-resolution photoemission spectroscopy of NaxCoO2.yH2O:Evidence for pseudogap formation

Abstract

We have studied the temperature-dependent electronic structure near the Fermi level (EF) of the layered cobaltate superconductor, Na0.35CoO2.1.3H2O, and related materials, using laser-excited ultrahigh-resolution photoemission spectroscopy. We observe the formation of a pseudogap with an energy scale of ~ 20 meV in Na0.35CoO2.1.3H2O and Na0.35CoO2.0.7H2O, which is clearly absent in Na0.7CoO2. The energy scale of the pseudogap is larger than the expected value for the superconducting gap, suggesting an additional competing order parameter at low temperatures. We discuss implications of the pseudogap in relation to available transport and magnetic susceptibility results.

4 pages, 3 figures

References in corpus (4)

• Fermi surface and quasiparticle dynamics of Na(x)CoO2 {x=0.7} investigated by Angle-Resolved Photoemission Spectroscopy
• ARPES on Na${}_{0.6}$CoO${}_2$: Fermi surface, extended flat dispersion, and unusual band splitting
• Charge Disproportionation and Spin Ordering Tendencies in Na(x)CoO2
• Superconducting Properties under Magnetic Field in Na${}_{0.35}$CoO${}_2\cdot 1.3$H${}_2$O Single Crystal

Cited by in corpus (13)

• Origin of the Weak Pseudo-gap Behaviors in Na_{0.35}CoO_2: Absence of Small Hole Pockets
• Low-Temperature and High-Energy-Resolution Laser Photoemission Spectroscopy
• Anomalous electronic Raman scattering in Na_xCoO_2 H_2O
• Mottness on a triangular lattice
• ${}^{17}$O NMR Measurements on Superconducting Na${}_{0.35}$CoO${}_2\cdot y$H${}_2$O
• Anisotropic Behavior of Knight Shift in Superconducting State of Na_xCoO_2yH_2O
• s-wave Superconductivity due to Suhl-Kondo Mechanism in Na${}_x$CoO${}_2\cdot y$H${}_2$O: Effect of Coulomb Interaction and Trigonal Distortion
• Electron-phonon interaction dressed by electronic correlations near charge ordering as the origin for superconductivity in cobaltates
• Band structure renormalization and weak pseudogap behavior in Na_{0.33}CoO_2: Fluctuation exchange study based on a single band model
• Charge order and phonon renormalizations: Possible implications for cobaltates
• One-particle spectral properties of the t-J-$V$ model on the triangular lattice near charge order
• Unconventional superconductivity in NaxCoO2 yH2O
• Evolution of electron Fermi surface with doping in cobaltates