It is now well established that superconducting cuprates support a charge-density-wave state in the so-called underdoped region of their phase diagram. We investigate the possibility of charge order in the square-lattice Hubbard model, both alone and in coexistence with d-wave superconductivity. The charge order has a period of 4 in one direction, is centered on bonds, and has a d form factor. We use the variational cluster approximation, an approach based on a rigorous variational principle that treats short-range correlations exactly, with two clusters of size 2 × 6 that together tile the infinite lattice and provide a nonbiased unit for a period-4 bond-density wave (BDW). We find that the BDW exists in a finite range of hole doping and increases in strength from U = 5 to U = 8. Its location and intensity depend strongly on the band dispersion. When probed simultaneously with d-wave superconductivity, the energy is sometimes lowered by the presence of both phases, depending on the interaction strength. Whenever they coexist, a pair-density wave (a modulation of superconducting pairing with the same period and form factor as the BDW) also exists.

%B Phys. Rev. B %V 95 %P 115127 %G eng %U http://journals.aps.org/prb/pdf/10.1103/PhysRevB.95.115127 %R 10.1103/PhysRevB.95.115127 %0 Journal Article %J Phys. Rev. B %D 2017 %T Phenomenological theories of the low-temperature pseudogap: Hall number, specific heat, and Seebeck coefficient %A Verret, S. %A Simard, O. %A Charlebois, M. %A D. Sénéchal %A A.-M. S. Tremblay %B Phys. Rev. B %V 96 %P 125139 Editor's choice %8 Sep %G eng %U https://link.aps.org/doi/10.1103/PhysRevB.96.125139 %R 10.1103/PhysRevB.96.125139 %0 Journal Article %J Physical Review B %D 2017 %T Pseudogap-to-metal transition in the anisotropic two-dimensional Hubbard model %A Faye, J. P. L. %A D. Sénéchal %B Physical Review B %V 96 %G eng %U https://link.aps.org/doi/10.1103/PhysRevB.96.195114 %R 10.1103/PhysRevB.96.195114 %0 Journal Article %J Phys. Rev. B %D 2017 %T Subgap structures and pseudogap in cuprate superconductors: Role of density waves %A Verret, S %A Charlebois, M %A D. Sénéchal %A A.-M. S. Tremblay %XIn scanning tunneling microscopy conductance curves, the superconducting gap of cuprates is sometimes accompanied by small subgap structures at very low energy. This was documented early on near vortex cores and later at zero magnetic field. Using mean-field toy models of coexisting d-wave superconductivity, d-form-factor density wave, and extended s-wave pair density wave (s PDW), we find agreement with this phenomenon, with s PDW playing a critical role. We explore the high variability of the gap structure with changes in band structure and density wave (DW) wave vector, thus explaining why subgap structures may not be a universal feature in cuprates. In the absence of nesting, nonsuperconducting results never show signs of pseudogap, even for large density wave magnitudes, therefore reinforcing the idea of a distinct origin for the pseudogap, beyond mean-field theory. Therefore, we also briefly consider the effect of DWs on a preexisting pseudogap.

%B Phys. Rev. B %V 95 %P 054518 %G eng %R 10.1103/PhysRevB.95.054518 %0 Journal Article %J Phys. Rev. B %D 2016 %T Kekulé superconductivity and antiferromagnetism on the graphene lattice %A Faye, J. P. L. %A Diarra, M. N. %A D. Sénéchal %B Phys. Rev. B %V 93 %G eng %N 15 %& 155149 %R 10.1103/PhysRevB.93.155149 %0 Journal Article %J Phys. Rev. B %D 2016 %T Mott transition and magnetism on the anisotropic triangular lattice %A Acheche, S. %A Reymbaut, A. %A Charlebois, M. %A D. Sénéchal %A A.-M. S. Tremblay %B Phys. Rev. B %V 94 %P 245133 %8 Dec %G eng %U http://link.aps.org/doi/10.1103/PhysRevB.94.245133 %R 10.1103/PhysRevB.94.245133 %0 Journal Article %J Phys. Rev. B %D 2016 %T Quantum cluster approach to the spinful Haldane-Hubbard model %A Wu, Jingxiang %A Faye, Jean Paul Latyr %A D. Sénéchal %A Maciejko, Joseph %B Phys. Rev. B %I American Physical Society %V 93 %P 075131 %8 Feb %U http://link.aps.org/doi/10.1103/PhysRevB.93.075131 %R 10.1103/PhysRevB.93.075131 %0 Journal Article %J Physical Review B %D 2015 %T Chiral triplet superconductivity on the graphene lattice %A Faye, J. P. L. %A P. Sahebsara %A D. Sénéchal %B Physical Review B %V 92 %8 8/2015 %N 8 %! Phys. Rev. B %R 10.1103/PhysRevB.92.085121 %0 Journal Article %J Physical Review B %D 2015 %T d-wave superconductivity in coupled ladders %A Faye, J. P. L. %A Hassan, S. R. %A Sriluckshmy, P. V. %A Baskaran, G. %A D. Sénéchal %B Physical Review B %V 91 %8 5/2015 %N 19 %! Phys. Rev. B %R 10.1103/PhysRevB.91.195126 %0 Journal Article %J Phys. Rev. B %D 2015 %T Impurity-induced magnetic moments on the graphene-lattice Hubbard model: An inhomogeneous cluster dynamical mean-field theory study %A Charlebois, M. %A D. Sénéchal %A Gagnon, A.-M. %A A.-M. S. Tremblay %B Phys. Rev. B %I American Physical Society %V 91 %P 035132 %8 Jan %U http://link.aps.org/doi/10.1103/PhysRevB.91.035132 %R 10.1103/PhysRevB.91.035132 %0 Book Section %B Many-Body Physics: From Kondo to Hubbard, Lecture Notes of the Autumn School on Correlated Electrons 2015 %D 2015 %T Quantum cluster methods: CPT and CDMFT %A D. Sénéchal %E Pavarini, Eva %E Koch, Erik %E Piers Coleman %B Many-Body Physics: From Kondo to Hubbard, Lecture Notes of the Autumn School on Correlated Electrons 2015 %I Forschungszentrum Jülich %V 5 %P 13.1 - 13.32 %& 13 %0 Journal Article %J Physical Review B %D 2014 %T Topological phases of the Kitaev-Hubbard model at half filling %A Faye, J. P. L. %A D. Sénéchal %A Hassan, S. R. %B Physical Review B %V 89 %8 3/2014 %N 11 %! Phys. Rev. B %R 10.1103/PhysRevB.89.115130 %0 Journal Article %J Physical Review Letters %D 2013 %T Absence of Spin Liquid in Nonfrustrated Correlated Systems %A Hassan, S. R. %A D. Sénéchal %B Physical Review Letters %V 110 %8 2/2013 %N 9 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.110.096402 %0 Journal Article %J Physical Review Letters %D 2013 %T Hassan and Sénéchal Reply: %A Hassan, S. R. %A D. Sénéchal %B Physical Review Letters %V 111 %G eng %U http://www.scopus.com/inward/record.url?eid=2-s2.0-84880559675&partnerID=40&md5=8f53efbdf35067625da102ef8c9d1990 %0 Journal Article %J Phys. Rev. B %D 2013 %T Mott p-n junctions in layered materials %A Charlebois, M. %A Hassan, S. R. %A Karan, R. %A D. Sénéchal %A A.-M. S. Tremblay %B Phys. Rev. B %I American Physical Society %V 87 %P 035137 %8 Jan %U http://link.aps.org/doi/10.1103/PhysRevB.87.035137 %R 10.1103/PhysRevB.87.035137 %0 Journal Article %J Physical Review B %D 2013 %T Quarter-filled Kitaev-Hubbard model: A quantum Hall state in an optical lattice %A Hassan, S. R. %A Goyal, Sandeep %A Shankar, R. %A D. Sénéchal %B Physical Review B %V 88 %8 7/2013 %N 4 %! Phys. Rev. B %R 10.1103/PhysRevB.88.045301 %0 Journal Article %J Phys. Rev. B %D 2013 %T Resilience of d-wave superconductivity to nearest-neighbor repulsion %A D. Sénéchal %A Day, A. G. R. %A Bouliane, V. %A A.-M. S. Tremblay %B Phys. Rev. B %I American Physical Society %V 87 %P 075123 %8 Feb %U http://link.aps.org/doi/10.1103/PhysRevB.87.075123 %R 10.1103/PhysRevB.87.075123 %0 Journal Article %J Physical Review Letters %D 2013 %T Stable Algebraic Spin Liquid in a Hubbard Model %A Hassan, S. %A Sriluckshmy, P. %A Goyal, Sandeep %A Shankar, R. %A D. Sénéchal %B Physical Review Letters %V 110 %8 1/2013 %N 3 %! Phys. Rev. Lett. %R 10.1103/PhysRevLett.110.037201 %0 Book Section %B Theoretical methods for Strongly Correlated Systems %D 2012 %T Cluster Dynamical Mean Field Theory %A D. Sénéchal %E Adolfo Avella %E Ferdinando Mancini %B Theoretical methods for Strongly Correlated Systems %S Springer Series in Solid-State Sciences %I Springer %V 171 %P 341–370 %G eng %& 11 %0 Book Section %B Theoretical methods for Strongly Correlated Systems %D 2012 %T Cluster Perturbation Theory %A D. Sénéchal %E Adolfo Avella %E Ferdinando Mancini %B Theoretical methods for Strongly Correlated Systems %S Springer Series in Solid-State Sciences %I Springer %V 171 %P 237–269 %G eng %& 8 %0 Journal Article %J Physical Review B %D 2011 %T d-wave superconductivity on the checkerboard Hubbard model at weak and strong coupling %A Shiladitya Chakraborty %A D. Sénéchal %A A.-M. S. Tremblay %B Physical Review B %V 84 %P 054545/1--8 %8 2011 %& 054545 %0 Journal Article %J Physics in Canada/La physique au Canada %D 2011 %T Superconductivity in the subatomic realm %A D. Sénéchal %B Physics in Canada/La physique au Canada %V 67 %8 April-June %G eng %0 Journal Article %J Phys. Rev. B %D 2011 %T Variational cluster approximation study of the one-dimensional Holstein-Hubbard model at half filling %A Payeur, Alexandre %A D. Sénéchal %B Phys. Rev. B %I American Physical Society %V 83 %P 033104 %8 Jan %G eng %R 10.1103/PhysRevB.83.033104 %0 Journal Article %J Physical Review B %D 2010 %T Bath optimization in the cellular dynamical mean-field theory %A D. Sénéchal %K Sans titre %B Physical Review B %I American Physical Society %V 81 %P 235125 %8 Jun %G eng %R 10.1103/PhysRevB.81.235125 %0 Journal Article %J Physical Review B (Editor's choice) %D 2010 %T Dynamical electronic nematicity from Mott physics %A Okamoto, S. %A D. Sénéchal %A Civelli, M. %A A.-M. S. Tremblay %XVery large anisotropies in transport quantities have been observed in the presence of very small in-plane structural anisotropy in many strongly correlated electron materials. By studying the two-dimensional Hubbard model with dynamical-mean-field theory for clusters, we show that such large anisotropies can be induced without static stripe order if the interaction is large enough to yield a Mott transition. Anisotropy decreases at large frequency. The maximum effect on conductivity anisotropy occurs in the underdoped regime, as observed in high-temperature superconductors.

%B Physical Review B (Editor's choice) %V 82 %P 180511(R)/1-4 %8 2010 %G eng %0 Journal Article %J Europhysics Letters %D 2009 %T First-order Mott transition at zero temperature in two dimensions: Variational plaquette study %A Balzer, M. %A B. Kyung %A D. Sénéchal %A A.-M. S. Tremblay %A Potthoff, M. %XThe nature of the metal-insulator Mott transition at zero temperature has been discussed for a number of years. Whether it occurs through a quantum critical point or through a first-order transition is expected to profoundly influence the nature of the finite-temperature phase diagram. In this paper, we study the zero temperature Mott transition in the two-dimensional Hubbard model on the square lattice with the variational cluster approximation. This takes into account the influence of antiferromagnetic short-range correlations. By contrast to single-site dynamical mean-field theory, the transition turns out to be first order even at zero temperature. Copyright (C) EPLA, 2009

%B Europhysics Letters %V 85 %P 17002/1-6 %8 2009 %G eng %0 Journal Article %J Physical Review B %D 2009 %T Pairing dynamics in strongly correlated superconductivity %A B. Kyung %A D. Sénéchal %A A.-M. S. Tremblay %XConfirmation of the phononic origin of Cooper pair formation in superconductors came with the demonstration that the interaction was retarded and that the corresponding energy scales were associated with phonons. Using cellular dynamical mean-field theory for the two-dimensional Hubbard model, we identify such retardation effects in d-wave pairing and associate the corresponding energy scales with short-range spin fluctuations. We find which frequencies are relevant for pairing as a function of interaction strength and doping and show that the disappearance of superconductivity on the overdoped side coincides with the disappearance of the low-energy feature in the antiferromagnetic fluctuations, as observed in neutron-scattering experiments.

%B Physical Review B %V 80 %P 205109/1-8 %8 2009 %G eng %0 Journal Article %J Physical Review B %D 2008 %T Anomalous superconductivity and its competition with antiferromagnetism in doped Mott insulators %A Kancharla, S. S. %A B. Kyung %A D. Sénéchal %A Civelli, M. %A Capone, M. %A Kotliar, G. %A A.-M. S. Tremblay %XProximity to a Mott insulating phase is likely to be an important physical ingredient of a theory that aims to describe high-temperature superconductivity in the cuprates. Quantum cluster methods are well suited to describe the Mott phase. Hence, as a step toward a quantitative theory of the competition between antiferromagnetism and d-wave superconductivity in the cuprates, we use cellular dynamical mean-field theory to compute zero-temperature properties of the two-dimensional square lattice Hubbard model. The d-wave order parameter is found to scale like the superexchange coupling J for on-site interaction U comparable to or larger than the bandwidth. The order parameter also assumes a dome shape as a function of doping, while, by contrast, the gap in the single-particle density of states decreases monotonically with increasing doping. In the presence of a finite second neighbor hopping t', the zero-temperature phase diagram displays the electron-hole asymmetric competition between antiferromagnetism and superconductivity that is observed experimentally in the cuprates. Adding realistic third neighbor hopping t '' improves the overall agreement with the experimental phase diagram. Since band parameters can vary depending on the specific cuprate considered, the sensitivity of the theoretical phase diagram to band parameters challenges the commonly held assumption that the doping Vs T-c/T-c(max) phase diagram of the cuprates is universal. The calculated angle-resolved photoemission spectrum displays the observed electron-hole asymmetry. The tendency to homogeneous coexistence of the superconducting and antiferromagnetic order parameters is stronger than observed in most experiments but consistent with many theoretical results and with experiments in some layered high-temperature superconductors. Clearly, our calculations reproduce important features of d-wave superconductivity in the cuprates that would otherwise be considered anomalous from the point of view of the standard Bardeen-Cooper-Schrieffer approach. At strong coupling, d-wave superconductivity and antiferromagnetism naturally appear as two equally important competing instabilities of the normal phase of the same underlying Hamiltonian.

%B Physical Review B %V 77 %P 184516/1-12 %8 2008 %G eng %0 Journal Article %J Physical Review B %D 2008 %T Convexity of the self-energy functional in the variational cluster approximation %A Nevidomskyy, A. H. %A D. Sénéchal %A A.-M. S. Tremblay %XIn the variational cluster approximation (VCA) (or variational cluster perturbation theory), widely used to study the Hubbard model, a fundamental problem that renders variational solutions difficult in practice is its known lack of convexity at stationary points, i.e., the physical solutions can be saddle points rather than extrema of the self-energy functional. Here, we suggest two different approaches to construct a convex functional Omega[Sigma]. In the first approach, one can show analytically that in the approximation where the irreducible particle-hole vertex depends only on center of mass coordinates, the functional is convex away from phase transitions in the corresponding channel. Numerical tests on a tractable version of that functional show that convexity can be a nuisance when looking for instabilities both in the pairing and particle-hole channels. Therefore, an alternative phenomenological functional is proposed. Convexity is explicitly enforced only with respect to a restricted set of variables, such as the cluster chemical potential that is known to be otherwise problematic. Numerical tests show that our functional is convex at the physical solutions of VCA and allows second-order phase transitions in the pairing channel as well. This opens the way to the use of more efficient algorithms to find solutions of the VCA equations.

%B Physical Review B %V 77 %P 075105/1-12 %8 2008 %G eng %0 Journal Article %J Physical Review Letters %D 2008 %T Hubbard Model on the Triangular Lattice: Spiral Order and Spin Liquid %A P. Sahebsara %A D. Sénéchal %K Sans titre %B Physical Review Letters %V 100 %P 136402 %G eng %0 Journal Article %J Physical Review B %D 2008 %T Magnetism and d-wave superconductivity on the half-filled square lattice with frustration %A Nevidomskyy, A. H. %A Scheiber, C. %A D. Sénéchal %A A.-M. S. Tremblay %XThe role of frustration and interaction strength on the half-filled Hubbard model is studied on the square lattice with nearest- and next-nearest-neighbor hoppings t and t(') using the variational cluster approximation (VCA). At half-filling, we find two phases with long-range antiferromagnetic (AF) order: the usual Neel phase, stable at small frustration t(')/t, and the so-called collinear (or superantiferromagnet) phase with ordering wave vector (pi,0) or (0,pi), stable for large frustration. These are separated by a phase with no detectable long-range magnetic order. We also find the d-wave superconducting (SC) phase (d(x)(2)-y(2)), which is favored by frustration if it is not too large. Intriguingly, there is a broad region of coexistence where both AF and SC order parameters have nonzero values. In addition, the physics of the metal-insulator transition in the normal state is analyzed. The results obtained with the help of the VCA method are compared with the large-U expansion of the Hubbard model and known results for the frustrated J(1)-J(2) Heisenberg model. These results are relevant for pressure studies of undoped parents of the high-temperature superconductors: we predict that an insulator to d-wave SC transition may appear under pressure.

%B Physical Review B %V 77 %P 064427/1-13 %8 2008 %G eng %0 Journal Article %J New Journal of Physics %D 2008 %T Is SUSY natural? %A K. Dienes %A Michael Lennek %A D. Sénéchal %A Vaibhav Wasnik %K Sans titre %XSpace-time supersymmetry (SUSY) is widely believed to play an important role in most fundamental theories of physics, and is usually invoked in order to address problems of naturalness. In this paper, we examine the question of whether SUSY itself is ’natural’ (i.e. likely to exist as a fundamental component of nature at high-energy scales). Our approach to answering this question is based on a statistical examination of the heterotic string landscape, and our conclusion is that SUSY is an exceedingly rare phenomenon. We also find that the likelihood of SUSY appearing at the string scale is dependent on the gauge symmetries present at the string scale, with certain gauge groups strongly favoring the appearance of {\\cal N} = 1 SUSY and others not. This paper summarizes several recent papers, yet also contains some new results. In particular, one new result is that the heterotic landscape appears to favor either the non-supersymmetric Standard Model or an {\\cal N} =1 SUSY GUT gauge group at the string scale; by contrast, the opposite outcomes (namely the minimal supersymmetric Standard Model (MSSM) or a non-supersymmetric GUT) are significantly disfavored.

%B New Journal of Physics %V 10 %P 085003 (10pp) %G eng %0 Journal Article %J High Performance Computing Systems and Applications, 2008. HPCS 2008. 22nd International Symposium on %D 2008 %T The Variational Cluster Approximation for Hubbard Models: Practical Implementation %A D. Sénéchal %K correlated electron systems %K frequency- wavevector integrals %K high-temperature superconductors %K Hubbard model %K integral equations %K lattice sites %K lattice theory %K molecular electronic states %K organic superconductors %K organic superconductorsHubbard models %K Sans titre %K senechal %K variational cluster approximation %B High Performance Computing Systems and Applications, 2008. HPCS 2008. 22nd International Symposium on %P 9-15 %8 June %G eng %R 10.1109/HPCS.2008.18 %0 Journal Article %J Phys. Rev. D %D 2007 %T Supersymmetry versus gauge symmetry on the heterotic landscape %A K. Dienes %A Michael Lennek %A D. Sénéchal %A Vaibhav Wasnik %K Sans titre %B Phys. Rev. D %V 75 %P 126005 %G eng %0 Journal Article %J Physical Review Letters %D 2006 %T Antiferromagnetism and Superconductivity in Layered Organic Conductors: Variational Cluster Approach %A P. Sahebsara %A D. Sénéchal %K Sans titre %B Physical Review Letters %V 97 %P 257004 %G eng %0 Journal Article %J Iranian Journal of Physics Research %D 2006 %T d-wave superconductivity, antiferromagnetism and spin liquid in quasi-two-dimensional organic superconductors %A P. Sahebsara %A D. Sénéchal %K Sans titre %B Iranian Journal of Physics Research %V 6 %P 179–186 %G eng %0 Journal Article %J Low Temperature Physics %D 2006 %T Pseudogap and high-temperature superconductivity from weak to strong coupling. Towards a quantitative theory %A A.-M. S. Tremblay %A B. Kyung %A D. Sénéchal %XThis is a short review of the theoretical work on the two-dimensional Hubbard model performed in Sherbrooke in the last few years. It is written on the occasion of the twentieth anniversary of the discovery of high-temperature superconductivity. We discuss several approaches, how they were benchmarked and how they agree sufficiently with each other that we can trust that the results are accurate solutions of the Hubbard model. Then comparisons are made with experiment. We show that the Hubbard model does exhibit d-wave superconductivity and antiferromagnetism essentially where they are observed for both hole- and electron-doped cuprates. We also show that the pseudogap phenomenon comes out of these calculations. In the case of electron-doped high temperature superconductors, comparisons with angle-resolved photoemission experiments are nearly quantitative. The value of the pseudogap temperature observed for these compounds in recent photoemission experiments had been predicted by theory before it was observed experimentally. Additional experimental confirmation would be useful. The theoretical methods that are surveyed include mostly the two-particle self-consistent approach, variational cluster perturbation theory (or variational cluster approximation), and cellular dynamical mean-field theory. (c) 2006 American Institute of Physics.

%B Low Temperature Physics %V 32 %P 424–451 %G eng %0 Journal Article %J Physical Review B %D 2006 %T Pseudogap induced by short-range spin correlations in a doped Mott insulator %A B. Kyung %A Kancharla, S. S. %A D. Sénéchal %A A.-M. S. Tremblay %A Civelli, M. %A Kotliar, G. %XWe study the evolution of a Mott-Hubbard insulator into a correlated metal upon doping in the two-dimensional Hubbard model using the cellular dynamical mean-field theory. Short-range spin correlations create two additional bands apart from the familiar Hubbard bands in the spectral function. Even a tiny doping into this insulator causes a jump of the Fermi energy to one of these additional bands and an immediate momentum-dependent suppression of the spectral weight at this Fermi energy. The pseudogap is closely tied to the existence of these bands. This suggests a strong-coupling mechanism that arises from short-range spin correlations and large scattering rates for the pseudogap phenomenon seen in several cuprates.

%B Physical Review B %V 73 %P 1651114/1-6 %8 2006 %G eng %0 Journal Article %J Journal of Physics and Chemistry of Solids %D 2006 %T Strong- and weak-coupling mechanisms for pseudogap in electron-doped cuprates %A Hankevych, V. %A B. Kyung %A Dare, A. M. %A D. Sénéchal %A A.-M. S. Tremblay %XUsing the two-particle self-consistent approach and cluster perturbation theory for the two-dimensional t-t'-t"-U Hubbard model, we discuss weak- and strong-coupling mechanisms for the pseudogap observed in recent angle resolved photoemission spectroscopy on electron-doped cuprates. In the case of the strong-coupling mechanism, which is more relevant near half-filling, the pseudogap can be mainly driven by short-range correlations near the Mott insulator. In the vicinity of optimal doping, where weak-coupling physics is more relevant, large antiferromagnetic correlation lengths, seen in neutron measurements, are the origin of the pseudogap. The t-J model is not applicable in the latter case. (c) 2006 Elsevier Ltd. All rights reserved.

%B Journal of Physics and Chemistry of Solids %V 67 %P 189–192 %G eng %0 Journal Article %J Physical Review Letters %D 2005 %T Competition between Antiferromagnetism and Superconductivity in High-$T_c$ Cuprates %A D. Sénéchal %A P.-L. Lavertu %A M.-A. Marois %A A.-M. S. Tremblay %K Sans titre %B Physical Review Letters %V 94 %P 156404/1-4 %8 2005 %G eng %& 156404 %0 Journal Article %J Physical Review Letters %D 2004 %T Hot spots and pseudogaps for hole- and electron-doped high-temperature superconductors %A D. Sénéchal %A A.-M. S. Tremblay %XUsing cluster perturbation theory, it is shown that the spectral weight and pseudogap observed at the Fermi energy in recent angle resolved photoemission spectroscopy of both electron- and hole-doped high-temperature superconductors find their natural explanation within the t-t(')-t('')-U Hubbard model in two dimensions. The value of the interaction U needed to explain the experiments for electron-doped systems at optimal doping is in the weak to intermediate coupling regime where the t-J model is inappropriate. At strong coupling, short-range correlations suffice to create a pseudogap, but at weak-coupling long correlation lengths associated with the antiferromagnetic wave vector are necessary.

%B Physical Review Letters %V 92 %P 126401/1-4 %8 2004 %G eng %0 Conference Proceedings %B Spectroscopies in Novel Superconductors %D 2004 %T Strong- and weak-coupling mechanisms for pseudogap in electron-doped cuprates %A Hankevych, Vasyl %A Kyung, Bumsoo %A Daré, A.-M. %A D. Sénéchal %A A.-M. S. Tremblay %B Spectroscopies in Novel Superconductors %V Journal of Physics and Chemistry of Solids : 67 %P 189-192 %8 2006 %0 Book Section %D 2004 %T Theoretical Methods For Strongly Correlated Electrons %A S. Allen %A A.-M. S. Tremblay %A Vilk, Y.M. %E D. Sénéchal %E A.-M. S. Tremblay %E C Bourbonnais %XThe conserving approximation scheme to many-body problems was developed by Kadanoff and Baym using the functional-derivative approach. Another approach for the Hubbard model also satisfies conservation laws, but in addition it satisfies the Pauli principle and a number of sum rules. A concise formal derivation of that approach, using functional derivatives, is given in this conference paper to highlight formal analogies and differences with conserving approximations.

%I Springer %P 341–355 %G eng %& Conserving approximations vs. two-particle self-consistent approach %0 Conference Paper %B High Performance Computing Systems and Applications and OSCAR symposium %D 2003 %T A cluster method for spectral properties of correlated electrons %A D. Sénéchal %E D. Sénéchal %K Sans titre %B High Performance Computing Systems and Applications and OSCAR symposium %I NRC Press, Ottawa %G eng %0 Book %B CRM Series in Mathematical Physics %D 2003 %T Theoretical Methods for Strongly Correlated Electrons %A D. Sénéchal %A A.-M. S. Tremblay %A C Bourbonnais %B CRM Series in Mathematical Physics %I 2003 %C New York %V Springer %P 361 %0 Conference Proceedings %B 17th annual international symposium on High Performance Computing Systems and Applications and the OSCAR Symposium %D 2003 %T What is the Hamiltonian for parent high-temperature superconductors? %A Alexis Gagné-Lebrun %A A.-M. S. Tremblay %E D. Sénéchal %B 17th annual international symposium on High Performance Computing Systems and Applications and the OSCAR Symposium %S NRC-CNRC Research Press, Ottawa %I NRC-CNRC Research Press, Ottawa %V Proceedings of the 17th annual international symposium on High Performance Computing Systems and Applications and the OSCAR Symp %P 71-77 %8 2003 %0 Journal Article %J Physical Review B %D 2002 %T Cluster Perturbation Theory for Hubbard models %A D. Sénéchal %A D. Perez %A D. Plouffe %K Sans titre %B Physical Review B %V 66 %P 075129 %G eng %0 Book Section %B Theoretical Methods for Strongly Correlated Electrons %D 2001 %T Conserving approximations vs Two-Particle Self-Consistent Approach %A S. Allen %A A.-M. S. Tremblay %A Vilk, Y.M. %E D. Sénéchal %E A.-M. S. Tremblay %E C Bourbonnais %B Theoretical Methods for Strongly Correlated Electrons %S CRM Series in Mathematical Physics %I 2003 %V CRM Series in Mathematical Physics %P 341-355 %& 8 %0 Conference Paper %B Actes du 42e congrès de l’Association mathématique du Québec %D 2000 %T Les mathématiques et la physique du XXème siècle : quelques aspects %A D. Sénéchal %K Sans titre %B Actes du 42e congrès de l’Association mathématique du Québec %I Éditions Le Griffon d’argile %C Sainte-Foy, Québec %P 179–193 %G eng %0 Journal Article %J Physical Review Letters %D 2000 %T Spectral Weight of the Hubbard Model through Cluster Perturbation Theory %A D. Sénéchal %A D. Perez %A M Pioro-Ladrière %K Sans titre %B Physical Review Letters %V 84 %P 522-525 %G eng %0 Journal Article %J Physical Review B %D 2000 %T The spin-1 ladder : A bosonization study %A D. Allen %A D. Sénéchal %K Sans titre %B Physical Review B %V 61 %P 12134–12142 %G eng %0 Journal Article %J Physics in Canada/La physique au Canada %D 2000 %T Strong correlations in low dimensional conductors: What are they and where are the challenges? %A A.-M. S. Tremblay %A C Bourbonnais %A D. Sénéchal %K Sans titre %B Physics in Canada/La physique au Canada %P 229 %8 Sept./Oct. %G eng %0 Journal Article %J European Physical Journal B %D 2000 %T Strong-coupling perturbation theory of the Hubbard model %A Pairault, S. %A D. Sénéchal %A A.-M. S. Tremblay %K Sans titre %XThe strong-coupling perturbation theory of the Hubbard model is presented and carried out tu order (t/U)(5) for the one-particle Green function In arbitrary dimension. The spectral weight A(k,omega) is expressed as a Jacobi continued fraction and compared with new Monte-Carlo data of the one-dimensional, half-filled Hubbard model. Different regimes (insulator, conductor and short-range antiferromagnet) are identified in the temperature-hopping integral (T, t) plane. This work completes a first paper on the subject (Phys. Rev. Lett. 80, 5389 (1998)) by providing details on diagrammatic rules and higher-order results. In addition, the non half-filled case, infinite resummations of diagrams and the double occupancy are discussed. Various tests: of the method are also presented.

%B European Physical Journal B %V 16 %P 85–105 %G eng %0 Journal Article %J Physical Review B %D 1998 %T The Fermi liquid as a Renormalization-Group fixed point: the role of interference in the Landau channel %A Chitov, G.Y. %A D. Sénéchal %K Sans titre %B Physical Review B %V 57 %P 1444–1456 %G eng %0 Journal Article %J Physical Review B %D 1998 %T SO(5)-Symmetric description of the low-energy sector of a ladder system %A D.G. Shelton %A D. Sénéchal %K Sans titre %B Physical Review B %V 58 %P 6818–6830 %G eng %0 Journal Article %J Physical Review Letters %D 1998 %T Strong-coupling expansion for the Hubbard model %A Pairault, S. %A D. Sénéchal %A A.-M. S. Tremblay %XA strong-coupling expansion for models of correlated electrons in any dimension is presented. The method is applied to the Hubbard model in d dimensions and compared with numerical results in d = 1. Third order expansion of the Green's function suffices to exhibit both the Mott metal-insulator transition and a low-temperature regime where antiferromagnetic correlations are strong. It is predicted that some of the weak photoemission signals observed in one-dimensional systems such as SrCuO2 should become stronger as temperature increases away from the spin-charge separated state.

%B Physical Review Letters %V 80 %P 5389–5392 %G eng %0 Journal Article %J Phys. Rev. E %D 1998 %T Thermal phase diagrams of columnar liquid crystals %A G. Lamoureux %A Caillé, A. %A D. Sénéchal %K Sans titre %B Phys. Rev. E %V 58 %P 5898–5908 %G eng %0 Book %D 1997 %T Conformal Field Theory %A Di Francesco, P. %A P. Mathieu %A D. Sénéchal %K Sans titre %I Springer %G eng %0 Journal Article %J Physical Review B %D 1997 %T Non-Abelian bosonization of the frustrated antiferromagnetic spin-1/2 chain %A D. Allen %A D. Sénéchal %K Sans titre %B Physical Review B %V 55 %P 299–308 %G eng %0 Journal Article %J Physical Review B %D 1995 %T Renormalization-group study of interacting electrons %A Chitov, G.Y. %A D. Sénéchal %K Sans titre %B Physical Review B %V 52 %P 13487–13496 %G eng %0 Journal Article %J Physical Review B %D 1995 %T Semiclassical description of spin ladders %A D. Sénéchal %K Sans titre %B Physical Review B %V 52 %P 15319–15326 %G eng %0 Journal Article %J Physical Review B %D 1995 %T Semiclassical description of the frustrated antiferromagnetic chain %A D. Allen %A D. Sénéchal %K Sans titre %B Physical Review B %V 51 %P 6394–6401 %G eng %0 Journal Article %J Physical Review B %D 1995 %T Temperature dependence of the ESR spectrum of {$\rm CsNiCl_3$} %A Y. Trudeau %A D. Sénéchal %A Poirier, M. %K Sans titre %B Physical Review B %V 51 %P 334–341 %G eng %0 Journal Article %J Nucl. Phys. B %D 1993 %T Can fusion coefficients be calculated from the depth rule? %A A.N. Kirillov %A P. Mathieu %A D. Sénéchal %A M. Walton %K Sans titre %B Nucl. Phys. B %V 391 %G eng %0 Journal Article %J Physical Review B %D 1993 %T Haldane gap in the quasi-one-dimensional nonlinear $\sigma$ model %A D. Sénéchal %K Sans titre %B Physical Review B %V 48 %P 15880–15885 %G eng %0 Journal Article %J Physical Review B %D 1993 %T The mass gap of the nonlinear $\sigma$ model through the finite temperature effective action %A D. Sénéchal %K Sans titre %B Physical Review B %V 47 %P 8353–8356 (Rapid. Comm.) %G eng %0 Journal Article %J Physics Letters B %D 1992 %T Chern-Simons superconductivity without parity violation %A D. Sénéchal %B Physics Letters B %V 297 %P 138-143 %G eng %0 Conference Paper %B Proceedings of the 1992 CAP/NSERC workshop on integrable models, statistical models and quantum group, Kingston (Ontario) %D 1992 %T Chern-Simons superconductivity without parity violation %A D. Sénéchal %B Proceedings of the 1992 CAP/NSERC workshop on integrable models, statistical models and quantum group, Kingston (Ontario) %I World Scientific %G eng %0 Journal Article %J Int. J. Mod. Phys. A %D 1992 %T Field identification in nonunitary diagonal cosets %A P. Mathieu %A D. Sénéchal %A M. Walton %K Sans titre %B Int. J. Mod. Phys. A %V 7 Suppl. 1B %P 731–764 %G eng %0 Journal Article %J Modern Physics Letters A %D 1992 %T Integrability of the quantum KdV equation at $c= -2$ %A Di Francesco, P. %A P. Mathieu %A D. Sénéchal %K Sans titre %B Modern Physics Letters A %V 7 %P 701–707 %G eng %0 Journal Article %J Int. J. Mod. Phys. A %D 1991 %T Chaos in the Hermitian one-matrix model %A D. Sénéchal %K Sans titre %B Int. J. Mod. Phys. A %V 7 %P 1491–1506 %G eng %0 Journal Article %J Can. J. Phys. %D 1991 %T Gravité quantique et modèles de matrices %A D. Sénéchal %K Sans titre %B Can. J. Phys. %V 69 %P 837–854 %G eng %0 Conference Paper %B Nonlinear fields: classical, random, semi-classical, Proceedings of the 27th Karpacz winter school of Theoretical Physics %D 1991 %T KdV-type equations in subcritical strings %A P. Mathieu %A D. Sénéchal %E P. Garbaczewski et Z. Popowicz %B Nonlinear fields: classical, random, semi-classical, Proceedings of the 27th Karpacz winter school of Theoretical Physics %G eng %0 Journal Article %J Modern Physics Letters A %D 1991 %T Tachyonic Hermitian one-matrix models %A P. Mathieu %A D. Sénéchal %K Sans titre %B Modern Physics Letters A %V 6 %P 819–829 %G eng %0 Journal Article %J Physics Letters B %D 1991 %T A well-defined multicritical series in the Hermitian one-matrix model %A P. Mathieu %A D. Sénéchal %K Sans titre %B Physics Letters B %V 267 %P 475–480 %G eng %0 Journal Article %J Phys. Rev. D %D 1990 %T Induced Hopf term in the nonlinear $\sigma$ model %A Z. Hlousek %A D. Sénéchal %A S.-H. Tye %K Sans titre %B Phys. Rev. D %V 41 %P 3773–3784 %G eng %0 Journal Article %J Phys. Rev. D %D 1989 %T Search for four-dimensional string models %A D. Sénéchal %K Sans titre %B Phys. Rev. D %V 39 %P 3717–3730 %G eng %0 Conference Paper %B Proceedings of the APS Meeting at Salt Lake City %D 1987 %T Construction of four-dimensional string models %A Hikaru Kawai %A David C. Lewellen %A Joel A. Schwartz %A D. Sénéchal %A S.-H. Henry Tye %E Carleton DeTar %E James Ball %B Proceedings of the APS Meeting at Salt Lake City %I World Scientific %G eng