Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 54: Correlated Electrons: Charge Order

TT 54.12: Talk

Friday, March 21, 2025, 12:30–12:45, H33

Combined Cluster and Diagrammatic Method for Symmetry Broken Phases in Correlated Electron Systems — •Félix Fossati and Evgeny Stepanov — Ecole Polytechnique

In this work, we investigate dynamical symmetry breaking in correlated electron systems. To achieve this, we refine a theoretical approach called D-TRILEX [1-3], which constructs a diagrammatic expansion based on an interacting reference system, using a cluster problem as a reference. Traditional cluster methods account for short-range correlation effects within the cluster exactly but neglect correlations beyond the cluster size. Our approach addresses this limitation by self-consistently combining the non-perturbative treatment of short-range correlations with a diagrammatic description of long-range collective electronic fluctuations. We demonstrate the effectiveness of this method by applying it to the one-dimensional Hubbard model. Our results show that the cluster extension of D-TRILEX accurately captures the transitions to the charge density wave (CDW) and bond-ordered wave (BOW) phases, which are associated with local and non-local order parameters, respectively, across various regimes of electronic interactions. This implementation provides new insights into the role of non-local interactions in dynamical symmetry breaking, establishing D-TRILEX as a promising tool for investigating complex phases in strongly correlated systems.

[1] E. A. Stepanov et al., Phys. Rev. B 100, 205115 (2019);

[2] V. Harkov et al., Phys. Rev. B 103, 245123 (2021);

[3] M. Vandelli et al., SciPost Phys. 13, 036. (2022).

Keywords: Diagrammatic extension; DMFT; D-TRILEX; charge density wave; bond-ordered wave