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David Leboeuf - Laboratoire National des Champs Magnétiques Intenses, Toulouse

The rise and fall of the electron pocket in hole-doped cuprates


The discovery of quantum oscillations in high-Tc cuprates both in the overdoped and underdoped regime revealed the dramatic evolution of the Fermi surface across the phase diagram. In the overdoped regime, the Fermi surface is found to be a large hole cylinder occupying 65 % of the first Brillouin zone. In contrast, the dominant frequency found in quantum oscillation experiments in the underdoped regime is small, indicating the presence of a Fermi pocket. The fact that this low frequency quantum oscillations were observed in a metallic state characterized by a negative Hall coefficient demonstrated that this pocket is electron-like. A Fermi surface reconstruction, occurring at a critical hole concentration between p ∼ 0.25 and p ∼ 0.14, where a translationnal symmetry breaking order sets in, is the standard mechanism to produce such a Fermi surface transformation.

 

I will first review the different transport signatures of this Fermi surface reconstruction : how does it appear in thermoelectric properties, in the Hall effect and in the in-plane and out-of-plane resistivity. I will then present a doping dependence study of the normal-state Hall effect measured in magnetic fields up to 60 T for dopings 0.078 < p < 0.152, that shows how the reconstructed Fermi surface evolves as a function of doping. For p>0.08, the Hall coefficient features a sign change as a function of temperature due to the emergence of an electron pocket. Below p ∼ 0.08, the Hall coefficient is positive down to the lowest temperature. We attribute this change of behaviour to the loss of the electron pocket through a possible Lifshitz transition at p=0.08. This Lifshitz transition is shown to trigger a sudden drop in the conductivity, reflecting the loss of the high-mobility sheet of the Fermi surface. All these findings are consistent with a Fermi-surface reconstruction caused by a stripe order. Given enough time, I will finally conclude and hopefully start a discussion with some more recent data that brings important piece of information about the role of the magnetic field in the above experiments.

 

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