SciPost Thesis Link
| Title: | The effect of short-range fluctuations on the onset of the strong coupling pseudogap in the triangular lattice | |
| Author: | Pierre-Olivier Downey | |
| As Contributor: | Pierre-Olivier Downey | |
| Type: | Master's | |
| Field: | Physics | |
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| Approach: | Computational | |
| URL: | https://savoirs.usherbrooke.ca/handle/11143/19277 | |
| Degree granting institution: | Université de Sherbrooke | |
| Supervisor(s): | André-Marie Tremblay | |
| Defense date: | 2022-06-07 |
Abstract:
One of the main puzzles of strongly correlated electron physics is the strong coupling pseudogap, the central part of my master’s thesis. This problem was first introduced by the discovery of cuprates, a wide class of materials know for the high temperature superconductivity, having all in common some 2D CuO$_2$ planes. It didn’t take time to understand that the Hubbard model, a very simple model, could model quite well those materials. This model is now one of the main studied model in material physics, hoping one day to understand high temperature superconductivity. It is thought that understanding the pseudogap, as known as the normal state of superconductivity, we could understand this behavior. Some of the many mechanisms proposed to solve the pseudogap involve Mott physics and the formation of singlets[1]. However, the use of square lattice and small clusters for calculations has made it difficult to assess the effect of short-range magnetic fluctuations on the onset of a pseudogap. Furthermore, long range magnetic order has lead to question the existence of the Mott transition in the thermodynamic limit, as discussed in Ref. [2]. In my thesis (in french), I use dynamical cluster approximation on a triangular lattice Hubbard model and verify that a) the Widom line starts from a first order transition and extends to high temperature and exist in the thermodynamic limit; b) the loss of spectral weight in the metal to Mott insulator transition for strong interactions is momentum dependent, the hallmark of a pseudogap; c) the pseudogap at half filling is continuously connected to the hole doped and electron doped strong coupling pseudogaps; d) The antiferromagnetic Brillouin zone is not linked to the formation of the pseudogap; e) the Van Hove singularity is not linked to the onset of the pseudogap. The thesis ends by showing how a minimum of compressibility could prove the existence of the pseudogap in $\kappa$-ET organic compounds. [1]. G. Sordi, K. Haule, and A.-M. S. Tremblay. Phys. Rev. B, 84(7) :075161, 2011. [2]. A. Wietek, R. Rossi, F. Simkovic, M. Klett, P. Hansmann, M. Ferrero, E. M. Stoudenmire, T. Schäfer, and A. Georges, Phys. Rev. X 11, 041013, 2021.