Superfluidity in topologically nontrivial flat bands

Research output: Contribution to journalArticleScientificpeer-review

Researchers

Research units

  • Swiss Federal Institute of Technology Zurich

Abstract

Topological invariants built from the periodic Bloch functions characterize new phases of matter, such as topological insulators and topological superconductors. The most important topological invariant is the Chern number that explains the quantized conductance of the quantum Hall effect. Here we provide a general result for the superfluid weight Ds of a multiband superconductor that is applicable to topologically nontrivial bands with nonzero Chern number C. We find that the integral over the Brillouin-zone of the quantum metric, an invariant calculated from the Bloch functions, gives the superfluid weight in a flat band, with the bound Dsgreater than or equal to|C|. Thus, even a flat band can carry finite superfluid current, provided the Chern number is nonzero. As an example, we provide Ds for the time-reversal invariant attractive Harper–Hubbard model that can be experimentally tested in ultracold gases. In general, our results establish that a topologically nontrivial flat band is a promising concept for increasing the critical temperature of the superconducting transition.

Details

Original languageEnglish
Article number8944
Pages (from-to)1-9
Number of pages9
JournalNature Communications
Volume6
Publication statusPublished - 2015
MoE publication typeA1 Journal article-refereed

    Research areas

  • Chern number, flat band, multiband superconductors, room-temperature superconductivity, superfluid density, superfluidity, topological invariant

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