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Verfasst von:Veschgini, Kambis [VerfasserIn]   i
 Salmhofer, Manfred [VerfasserIn]   i
Titel:Low-energy effective theory at a quantum critical point of the two-dimensional Hubbard model
Titelzusatz:mean-field analysis
Verf.angabe:Kambis Veschgini and Manfred Salmhofer
E-Jahr:2018
Jahr:13 December 2018
Umfang:14 S.
Fussnoten:Gesehen am 06.11.2020
Titel Quelle:Enthalten in: Physical review
Ort Quelle:Woodbury, NY : Inst., 2016
Jahr Quelle:2018
Band/Heft Quelle:98(2018,23) Artikel-Nummer 235131, 14 Seiten
ISSN Quelle:2469-9969
Abstract:We complement previous functional renormalization group (fRG) studies of the two-dimensional Hubbard model by mean-field calculations. The focus falls on Van Hove filling and the hopping amplitude t′/t=0.341. The fRG data suggest a quantum critical point (QCP) in this region and in its vicinity a singular fermionic self-energy ImΣ(ω)/ω∼−|ω|−γ with γ≈0.26 [K-U. Giering and M. Salmhofer, Self-energy flows in the two-dimensional repulsive Hubbard model, Phys. Rev. B 86, 245122 (2012)]. Here we start a more detailed investigation of this QCP using a bosonic formulation for the effective action, where the bosons couple to the order parameter fields. To this end, we use the channel decomposition of the fermionic effective action developed in C. Husemann and M. Salmhofer, Efficient Parametrization of the Vertex Function, Omega-Scheme, and the (t, t')-Hubbard Model at Van Hove Filling, Phys. Rev. B 79, 195125 (2009), which allows us to perform Hubbard-Stratonovich transformations for all relevant order parameter fields at any given energy scale Ω. We stop the flow at a scale Ω where the correlations of the order parameter field are already pronounced, but the flow is still regular, and derive the effective boson theory. It contains d-wave superconducting, magnetic, and density-density interactions. We analyze the resulting phase diagram in the mean-field approximation. We show that the singular fermionic self-energy suppresses gap formation both in the superconducting and magnetic channel already at the mean-field level, thus rounding a first-order transition (without self-energy) to a quantum phase transition (with self-energy). We give a simple effective model that shows the generality of this effect. In the two-dimensional Hubbard model, the effective density-density interaction is peaked at a nonzero frequency, so that solving the mean-field equations already involves a functional equation instead of simply a matrix equation (on a technical level, similar to incommensurate phases). Within a certain approximation, we show that such an interaction leads to a short quasiparticle lifetime.
DOI:doi:10.1103/PhysRevB.98.235131
URL:Bitte beachten Sie: Dies ist ein Bibliographieeintrag. Ein Volltextzugriff für Mitglieder der Universität besteht hier nur, falls für die entsprechende Zeitschrift/den entsprechenden Sammelband ein Abonnement besteht oder es sich um einen OpenAccess-Titel handelt.

Volltext ; Verlag: http://dx.doi.org/10.1103/PhysRevB.98.235131
 Volltext: https://link.aps.org/doi/10.1103/PhysRevB.98.235131
 DOI: https://doi.org/10.1103/PhysRevB.98.235131
Datenträger:Online-Ressource
Sprache:eng
K10plus-PPN:1586046233
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