Pairing and non-Fermi liquid behavior in partially flat-band systems: Beyond nesting physics
Year: 2020
Type: article
Abstract: While many-body effects in flat-band systems are receiving renewed hot interest in condensed-matter physics for superconducting and topological properties as well as for magnetism, studies have primarily been restricted to multiband systems (with coexisting flat and dispersive bands). Here we focus on one-band systems where a band is ``partially flat,'' comprising flat and dispersive portions in $k$ space to reveal whether intriguing correlation effects can already arise on the simplest possible one-band level. For that, the two-dimensional repulsive Hubbard model is studied for two models having different flat areas in an intermediate-coupling regime with the dynamical mean-field theory combined with the fluctuation exchange approximation. We have a crossover from ferromagnetic to antiferromagnetic spin fluctuations as the band filling is varied and this triggers, for the model with a wider flat portion, a triplet-pair superconductivity favored over an unusually wide filling region, which is taken over by a sharply growing singlet pairing. For the model with a narrower flat portion, ${T}_{C}$ against filling exhibits an unusual double-peaked ${T}_{C}$ dome, associated with different numbers of nodes in the gap function having remarkably extended pairs in real space. We identify these as a manifestation of the physics outside the conventional nesting physics where only the pair scattering across the Fermi surface in designated (hot) spots is relevant. Another correlation effect arising from the flattened band is found in a non-Fermi-liquid behavior as detected in the momentum distribution function, frequency dependence of the self-energy, and spectral function. These indicate that unusual correlation physics can indeed occur in flat-band systems.
Institutions: Institut polytechnique de Grenoble, Centre National de la Recherche Scientifique, Institut Néel, The Institute for Solid State Physics, The University of Tokyo, The University of Tokyo, SLAC National Accelerator Laboratory, Stanford University, TU Wien, Washington University in St. Louis, Pasargad Institute for Advanced Innovative Solutions, Sharif University of Technology, National Institute of Advanced Industrial Science and Technology
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Funders: National Science Foundation, U.S. Department of Energy, Agence Nationale de la Recherche, Cabinet Office, Government of Japan, Council for Science, Technology and Innovation, Japan Society for the Promotion of Science, Japan Science and Technology Agency, Basic Energy Sciences, Core Research for Evolutional Science and Technology, Division of Materials Sciences and Engineering
Awards: Linear and non linear effects in driven 3D topological materials, G1286251239, G1579202703, Theoretical and experimental study of pressure and nonequilibrium control and enhancement of Tc based on the orbital distillation, G2371548206, G237429762, G303061748, G3702897590, G4656594441, G5570207115, G6550344761, G6718509927, Variety and universality of bulk-edge correspondence in topological phases: From solid state physics to transdisciplinary concepts, G7283024673, G7978616602, Theoretical Approaches to Multi-Scale Complex Systems, G8961514295, G911061179, G969889393
OpenAlex ID: W2925162007