| Autor: |
Nishchhal, Verma, Tamaghna, Hazra, Mohit, Randeria |
| Rok vydání: |
2021 |
| Předmět: |
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| Zdroj: |
Proc Natl Acad Sci U S A |
| ISSN: |
1091-6490 |
| Popis: |
We present exact results that give insight into how interactions lead to transport and superconductivity in a flat band where the electrons have no kinetic energy. We obtain bounds for the optical spectral weight for flat-band superconductors that lead to upper bounds for the superfluid stiffness and the two-dimensional (2D) [Formula: see text]. We focus on on-site attraction [Formula: see text] on the Lieb lattice with trivial flat bands and on the [Formula: see text]-flux model with topological flat bands. For trivial flat bands, the low-energy optical spectral weight [Formula: see text] with [Formula: see text] , where [Formula: see text] is the flat-band density and [Formula: see text] is the Marzari–Vanderbilt spread of the Wannier functions (WFs). We also obtain a lower bound involving the quantum metric. For topological flat bands, with an obstruction to localized WFs respecting all symmetries, we again obtain an upper bound for [Formula: see text] linear in [Formula: see text]. We discuss the insights obtained from our bounds by comparing them with mean-field and quantum Monte Carlo results. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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