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Low-Lying Quasiparticle States and Hidden Collective Charge Instabilities in Parent Cobaltate Superconductors

Qian, D. and Hsieh, D. and Wray, L. and Chuang, Y.-D. and Fedorov, A. and Wu, D. and Luo, J. L. and Wang, N. L. and Viciu, L. and Cava, R. J. and Hasan, M. Z. (2006) Low-Lying Quasiparticle States and Hidden Collective Charge Instabilities in Parent Cobaltate Superconductors. Physical Review Letters, 96 (21). Art. No. 216405. ISSN 0031-9007. doi:10.1103/PhysRevLett.96.216405.

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We report a state-of-the-art photoemission (angle-resolved photoemission spectroscopy) study of high quality single crystals of the Na_xCoO_2 series focusing on the fine details of the low-energy states. The Fermi velocity is found to be small (<0.5   eV    Å) and only weakly anisotropic over the Fermi surface at all dopings, setting the size of the pair wave function to be on the order of 10–20 nm. In the low-doping regime, the exchange interlayer splitting vanishes and two-dimensional collective instabilities such as 120°-type fluctuations become kinematically allowed. Our results suggest that the unusually small Fermi velocity and the unique symmetry of kinematic instabilities distinguish cobaltates from most other oxide superconductors.

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Hsieh, D.0000-0002-0812-955X
Additional Information:© 2006 The American Physical Society. Received 27 December 2005. Published 1 June 2006. We gratefully acknowledge P.W. Anderson, D. A. Huse, S. A. Kivelson, P. A. Lee, N. P. Ong, S. Shastry, and S. Sondhi for discussions. This work is partially supported through the NSFMRSEC (DMR-0213706), DOE Grants No. DE-FG02-05ER46200 and No. DE-FG02-98-ER45706, and NSFC (Grant No. 10574158). ALS is supported by DOE/BES-DEAC03-76SF00098.
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG02-05ER46200
Department of Energy (DOE)DE-FG02-98- ER45706
National Science Foundation of China (NSFC)10574158
Department of Energy (DOE)DEAC03-76SF00098
Issue or Number:21
Classification Code:PACS numbers: 71.20.Be, 71.30.+h, 73.20.At, 74.90.+n
Record Number:CaltechAUTHORS:20140908-085720745
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49311
Deposited By: Joy Painter
Deposited On:08 Sep 2014 17:37
Last Modified:10 Nov 2021 18:42

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