28 research outputs found
Coupled topological flat and wide bands: Quasiparticle formation and destruction
Flat bands amplify correlation effects and are of extensive current interest.
They provide a platform to explore both topology in correlated settings and
correlation physics enriched by topology. Recent experiments in correlated
kagome metals have found evidence for strange-metal behavior. A major
theoretical challenge is to study the effect of local Coulomb repulsion when
the band topology obstructs a real-space description. In a variant to the
kagome lattice, we identify an orbital-selective Mott transition for the first
time in any system of coupled topological flat and wide bands. This was made
possible by the construction of exponentially localized and Kramers-doublet
Wannier functions, which in turn leads to an effective Kondo lattice
description. Our findings show how quasiparticles are formed in such coupled
topological flat-wide band systems and, equally important, how they are
destroyed. Our work provides a conceptual framework for the understanding of
the existing and emerging strange-metal properties in kagome metals and beyond.Comment: 30 pages, 6 figures. To appear in Science Advance
Orbital-selective superconductivity in the nematic phase of FeSe
The interplay between electronic orders and superconductivity is central to
the physics of unconventional superconductors, and is particularly pronounced
in the iron-based superconductors. Motivated by recent experiments on FeSe, we
study the superconducting pairing in its nematic phase in a multiorbital model
with frustrated spin-exchange interactions. The electron correlations in the
presence of the nematic order give rise to an enhanced orbital selectivity in
the superconducting pairing amplitudes. This orbital-selective pairing produces
a large gap anisotropy on the Fermi surface. Our results naturally explain the
striking experimental observations, and shed new light on the unconventional
superconductivity of correlated electron systems in general.Comment: Final version as published in PRB, Rapid Communications. 6 pages with
4 figures, plus supplementary materia