Laser-excited ultrahigh-resolution photoemission spectroscopy of Na xCoO 2·yH 2O: Evidence for pseudogap formation

T. Shimojima; Takayoshi Yokoya; T. Kiss; A. Chainani; S. Shin; T. Togashi; S. Watanabe; C. Zhang; C. T. Chen; K. Takada; T. Sasaki; H. Sakurai; E. Takayama-Muromachi

doi:10.1103/PhysRevB.71.020505

Laser-excited ultrahigh-resolution photoemission spectroscopy of Na _xCoO ₂·yH ₂O: Evidence for pseudogap formation

T. Shimojima, Takayoshi Yokoya, T. Kiss, A. Chainani, S. Shin, T. Togashi, S. Watanabe, C. Zhang, C. T. Chen, K. Takada, T. Sasaki, H. Sakurai, E. Takayama-Muromachi

Research output: Contribution to journal › Article

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Abstract

We have studied the temperature (T)-dependent electronic structure near the Fermi level of the layered cobaltate superconductor, Na _0.35CoO ₂·1.3H ₂O, and related materials, using laser-excited ultrahigh-resolution photoemission spectroscopy. We observe the formation of a pseudogap (PG) with an energy scale of ∼20 meV in Na _0.35CoO ₂·1.3H ₂O and Na _0.35CoO ₂·0.7H ₂O, which is clearly absent in Na _0.7CoO ₂. The energy scale of the PG is larger than the expected value for the superconducting gap, suggesting an additional competing order parameter at low T. We discuss implications of the PG in relation to available transport and magnetic susceptibility results.

Original language	English
Article number	020505
Journal	Physical Review B - Condensed Matter and Materials Physics
Volume	71
Issue number	2
DOIs	https://doi.org/10.1103/PhysRevB.71.020505
Publication status	Published - Jan 2005
Externally published	Yes

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ASJC Scopus subject areas

Condensed Matter Physics

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Shimojima, T., Yokoya, T., Kiss, T., Chainani, A., Shin, S., Togashi, T., Watanabe, S., Zhang, C., Chen, C. T., Takada, K., Sasaki, T., Sakurai, H., & Takayama-Muromachi, E. (2005). Laser-excited ultrahigh-resolution photoemission spectroscopy of Na _xCoO ₂·yH ₂O: Evidence for pseudogap formation. Physical Review B - Condensed Matter and Materials Physics, 71(2), [020505]. https://doi.org/10.1103/PhysRevB.71.020505

Laser-excited ultrahigh-resolution photoemission spectroscopy of Na _xCoO ₂·yH ₂O : Evidence for pseudogap formation. / Shimojima, T.; Yokoya, Takayoshi; Kiss, T.; Chainani, A.; Shin, S.; Togashi, T.; Watanabe, S.; Zhang, C.; Chen, C. T.; Takada, K.; Sasaki, T.; Sakurai, H.; Takayama-Muromachi, E.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 71, No. 2, 020505, 01.2005.

Research output: Contribution to journal › Article

Shimojima, T, Yokoya, T, Kiss, T, Chainani, A, Shin, S, Togashi, T, Watanabe, S, Zhang, C, Chen, CT, Takada, K, Sasaki, T, Sakurai, H & Takayama-Muromachi, E 2005, 'Laser-excited ultrahigh-resolution photoemission spectroscopy of Na _xCoO ₂·yH ₂O: Evidence for pseudogap formation', Physical Review B - Condensed Matter and Materials Physics, vol. 71, no. 2, 020505. https://doi.org/10.1103/PhysRevB.71.020505

Shimojima, T. ; Yokoya, Takayoshi ; Kiss, T. ; Chainani, A. ; Shin, S. ; Togashi, T. ; Watanabe, S. ; Zhang, C. ; Chen, C. T. ; Takada, K. ; Sasaki, T. ; Sakurai, H. ; Takayama-Muromachi, E. / Laser-excited ultrahigh-resolution photoemission spectroscopy of Na _xCoO ₂·yH ₂O : Evidence for pseudogap formation. In: Physical Review B - Condensed Matter and Materials Physics. 2005 ; Vol. 71, No. 2.

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abstract = "We have studied the temperature (T)-dependent electronic structure near the Fermi level of the layered cobaltate superconductor, Na 0.35CoO 2·1.3H 2O, and related materials, using laser-excited ultrahigh-resolution photoemission spectroscopy. We observe the formation of a pseudogap (PG) with an energy scale of ∼20 meV in Na 0.35CoO 2·1.3H 2O and Na 0.35CoO 2·0.7H 2O, which is clearly absent in Na 0.7CoO 2. The energy scale of the PG is larger than the expected value for the superconducting gap, suggesting an additional competing order parameter at low T. We discuss implications of the PG in relation to available transport and magnetic susceptibility results.",

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AB - We have studied the temperature (T)-dependent electronic structure near the Fermi level of the layered cobaltate superconductor, Na 0.35CoO 2·1.3H 2O, and related materials, using laser-excited ultrahigh-resolution photoemission spectroscopy. We observe the formation of a pseudogap (PG) with an energy scale of ∼20 meV in Na 0.35CoO 2·1.3H 2O and Na 0.35CoO 2·0.7H 2O, which is clearly absent in Na 0.7CoO 2. The energy scale of the PG is larger than the expected value for the superconducting gap, suggesting an additional competing order parameter at low T. We discuss implications of the PG in relation to available transport and magnetic susceptibility results.

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10.1103/PhysRevB.71.020505