H. F. Fotso

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The dynamical cluster approximation (DCA) is a method which systematically incorporates nonlocal corrections to the dynamical mean-field approximation. Here we present a pedagogical discussion of the DCA by describing it as a ̊-derivable coarse-graining approximation in k-space, which maps an infinite lattice problem onto a periodic finite-sized cluster(More)
There is much interest in how quantum systems thermalize after a sudden change, because unitary evolution should preclude thermalization. The eigenstate thermalization hypothesis resolves this because all observables for quantum states in a small energy window have essentially the same value; it is violated for integrable systems due to the infinite number(More)
We use the dynamical cluster approximation to understand the proximity of the superconducting dome to the quantum critical point in the two-dimensional Hubbard model. In a BCS formalism, T(c) may be enhanced through an increase in the d-wave pairing interaction (V(d)) or the bare pairing susceptibility (χ(0d)). At optimal doping, where V(d) is revealed to(More)
The parquet formalism to calculate the two-particle Green’s functions of large systems requires the solution of a large, sparse, complex system of quadratic equations. If Nf Matsubara frequencies are used for a system of size Nc, and Newton’s method is used to solve the nonlinear system, the Jacobian system has O(8Nt ) variables and O(40Nt ) complex entries(More)
In many quantum architectures the solid-state qubits, such as quantum dots or color centers, are interfaced via emitted photons. However, the frequency of photons emitted by solid-state systems exhibits slow uncontrollable fluctuations over time (spectral diffusion), creating a serious problem for implementation of the photon-mediated protocols. Here we(More)
S.-X. Yang,1 H. Fotso,1 H. Hafermann,2 K.-M. Tam,1 J. Moreno,1 T. Pruschke,3 and M. Jarrell1 1Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA 2Centre de Physique Théorique, École Polytechnique, CNRS, FR-91128 Palaiseau Cedex, France 3Department of Physics, University of Göttingen, GE-37077 Göttingen,(More)
Time-of-flight images are a common tool in ultracold atomic experiments, employed to determine the quasimomentum distribution of the interacting particles. If one introduces a constant artificial electric field, then the quasimomentum distribution evolves in time as Bloch oscillations are generated in the system and then are damped, showing a complex series(More)
We present a numerical solution of the parquet approximation, a conserving diagrammatic approach which is self-consistent at both the single-particle and the two-particle levels. The fully irreducible vertex is approximated by the bare interaction thus producing the simplest approximation that one can perform with the set of equations involved in the(More)
We find that imposing crossing symmetry in the iteration process considerably extends the range of convergence for solutions of the parquet equations for the Hubbard model. When crossing symmetry is not imposed, the convergence of both simple iteration and more complicated continuous loading (homotopy) methods is limited to high temperatures and weak(More)
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