Alexander Lau, Sebastiano Peotta, Dmitry I. Pikulin, Enrico Rossi, Timo Hyart
SciPost Phys. 13, 086 (2022) ·
published 7 October 2022
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Motivated by the experimental progress in controlling the properties of the energy bands in superconductors, significant theoretical efforts have been devoted to study the effect of the quantum geometry and the flatness of the dispersion on the superfluid weight. In conventional superconductors, where the energy bands are wide and the Fermi energy is large, the contribution due to the quantum geometry is negligible, but in the opposite limit of flat-band superconductors the superfluid weight originates purely from the quantum geometry of Bloch wave functions. Here, we study how the energy band dispersion and the quantum geometry affect the disorder-induced suppression of the superfluid weight. In particular, we consider non-magnetic disorder and $s$-wave superconductivity. Surprisingly, we find that the disorder-dependence of the superfluid weight is universal across a variety of models, and independent of the quantum geometry and the flatness of the dispersion. Our results suggest that a flat-band superconductor is as resilient to disorder as a conventional superconductor.
SciPost Phys. 3, 041 (2017) ·
published 22 December 2017
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Semi-Dirac fermions are known to exist at the critical points of topological
phase transitions requiring fine-tuning of the parameters. We show that robust
semi-Dirac points can appear in a heterostructure consisting of superconducting
Sr2IrO4 and a t2g electron system (t2g-ES) without fine-tuning. They are
topologically stable in the presence of the symmetries of the model, metallic
t2g-ES and a single active band in Sr2IrO4. If the t2g metal is coupled to two
different layers of Sr2IrO4 (effectively a multiband superconductor) in a
three-layer-structure the semi-Dirac points can split into two stable Dirac
points with opposite chiralities. A similar transition can be achieved if the
t2g-ES supports intrinsic triplet superconductivity. By considering Sr2RuO4 as
an example of a t2g-ES we predict a rich topological phase diagram as a
function of various parameters.
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