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Séminaire LANEF - MCBT

Mardi 03 mars 2015 à 11h00,
Salle Louis Weil, E424

Orateur : Louis Taillefer (University of Sherbrooke, Canada)
"fermi-surface reconstruction by charge order in cuprate superconductors"


Since the discovery of quantum oscillations in 2007 [1], we know that the Fermi surface of the underdoped cuprate superconductor YBCO undergoes a reconstruction at low temperature. A signature of this reconstruction is the change of sign in the Hall [2] and Seebeck [3] coefficients, which become negative at low temperature. Observed in other hole-doped cuprates [3,4,5], this phenomenon is generic. By analogy with Eu-LSCO, where charge modulations are responsible for the reconstruction, a similar mechanism was inferred for YBCO [5]. Charge modulations in YBCO have since been observed directly by NMR [6] and X-ray diffraction [7,8,9]. Charge order has also been observed in other materials [10] – it represents a central new fact in the physics of cuprates.

We have used electrical, thermal and thermo-electric transport measurements in high magnetic fields to investigate the Fermi-surface reconstruction in YBCO and its impact on superconductivity. Based on our recent observation of a hole-like pocket in the Fermi surface of underdoped YBCO [11], I will argue that both charge order and the pseudogap play a role in the reconstruction. We have mapped out the upper critical field Hc2 as a function of doping across the phase diagram and find a dramatic drop in Hc2 below a critical doping p = 0.18 [12]. This shows that phase competition is what shapes the Tc dome in hole- doped cuprates.

[1] N. Doiron-Leyraud et al., Nature 447, 565 (2007).
[2] D. LeBoeuf et al., Nature 450, 533 (2007).
[3] J. Chang et al., Physical Review Letters 104, 057005 (2010).
[4] N. Doiron-Leyraud et al., Physical Review X 3, 021019 (2013).
[5] F. Laliberté et al., Nature Communications 2, 432 (2011).
[6] T. Wu et al., Nature 477, 191 (2011).
[7] G. Ghiringhelli et al., Science 337, 821 (2012).
[8] J. Chang et al., Nature Physics 8, 871 (2012).
[9] A. J. Achkar et al., Physical Review Letters 109, 167001 (2012).
[10] R. Comin et al., Science 343, 390 (2014).
[11] N. Doiron-Leyraud et al., Nature Communications (in press), arXiv:1409.2788.
[12] G. Grissonnanche et al., Nature Communications 5, 3280 (2014).

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