Superfluidity in topologically nontrivial flat bands
Citations Over TimeTop 10% of 2015 papers
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 Ds⩾|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.
Related Papers
- → Chern numbers hiding in time-of-flight images(2011)68 cited
- → Superfluid ultracold fermi gases(2007)45 cited
- → Superfluid density in continuous and discrete spaces: Avoiding misconceptions(2014)20 cited
- Detection of Chern numbers and entanglement in topological multi-component systems through subsystem winding numbers(2014)