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Updated: Aug 13, 2026

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures
Published on: October 9, 2012
Fermi surface and quasiparticle dynamics of Na0.7CoO2 investigated by angle-resolved photoemission spectroscopy
M Z Hasan1, Y-D Chuang, D Qian
1Joseph Henry Laboratories, Department of Physics, Princeton University, Princeton, New Jersey 08544, USA. mzhasan@Princeton.edu
Abstract:
We present the first angle-resolved photoemission study of Na0.7CoO2, the host material of the superconducting NaxCoO2.nH(2)O series. Our results show a hole-type Fermi surface, a strongly renormalized quasiparticle band, a small Fermi velocity, and a large Hubbard U. The quasiparticle band crosses the Fermi level from M toward Gamma suggesting a negative sign of effective single-particle hopping t(eff) (about 10 meV) which is on the order of magnetic exchange coupling J in this system. Quasiparticles are well defined only in the T-linear resistivity (non-Fermi-liquid) regime. Unusually small single-particle hopping and unconventional quasiparticle dynamics may have implications for understanding the phase of matter realized in this new class of a strongly interacting quantum system.
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The work...