Francis Laliberté

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The nature of the pseudogap phase is a central problem in the effort to understand the high-transition-temperature (high-T(c)) copper oxide superconductors. A fundamental question is what symmetries are broken when the pseudogap phase sets in, which occurs when the temperature decreases below a value T*. There is evidence from measurements of both polarized(More)
The origin of pairing in a superconductor resides in the underlying normal state. In the cuprate high-temperature superconductor YBa(2)Cu(3)O(y) (YBCO), application of a magnetic field to suppress superconductivity reveals a ground state that appears to break the translational symmetry of the lattice, pointing to some density-wave order. Here we use a(More)
It is still unclear why the transition temperature Tc of cuprate superconductors falls with underdoping. The doping dependence of the critical magnetic field Hc2 is directly relevant to this question, but different estimates of Hc2 are in sharp contradiction. We resolve this contradiction by tracking the characteristic field scale of superconducting(More)
In the quest to increase the critical temperature Tc of cuprate superconductors, it is essential to identify the factors that limit the strength of superconductivity. The upper critical field Hc2 is a fundamental measure of that strength, yet there is no agreement on its magnitude and doping dependence in cuprate superconductors. Here we show that the(More)
The Seebeck and Nernst coefficients S and nu of the cuprate superconductor YBa{2}Cu{3}O{y} (YBCO) were measured in a single crystal with doping p=0.12 in magnetic fields up to H=28 T. Down to T=9 K, nu becomes independent of field by H approximately 30 T, showing that superconducting fluctuations have become negligible. In this field-induced normal state,(More)
The pseudogap is a partial gap in the electronic density of states that opens in the normal (non-superconducting) state of cuprate superconductors and whose origin is a long-standing puzzle. Its connection to the Mott insulator phase at low doping (hole concentration, p) remains ambiguous and its relation to the charge order that reconstructs the Fermi(More)
The Nernst effect in metals is highly sensitive to two kinds of phase transition: superconductivity and density-wave order. The large, positive Nernst signal observed in hole-doped high-T(c) superconductors above their transition temperature (T(c)) has so far been attributed to fluctuating superconductivity. Here we report that in some of these materials(More)
David LeBoeuf,1,* Nicolas Doiron-Leyraud,1 B. Vignolle,2 Mike Sutherland,3,† B. J. Ramshaw,4 J. Levallois,2,‡ R. Daou,1,§ Francis Laliberté,1 Olivier Cyr-Choinière,1 Johan Chang,1 Y. J. Jo,5 L. Balicas,5 Ruixing Liang,4,6 D. A. Bonn,4,6 W. N. Hardy,4,6 Cyril Proust,2,6 and Louis Taillefer1,6,‖ 1Département de Physique and RQMP, Université de Sherbrooke,(More)
In underdoped cuprate superconductors, the Fermi surface undergoes a reconstruction that produces a small electron pocket, but whether there is another, as yet, undetected portion to the Fermi surface is unknown. Establishing the complete topology of the Fermi surface is key to identifying the mechanism responsible for its reconstruction. Here we report(More)
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