Dispersionless quantum states (“flat bands”) are counterintuitive: with the electron velocity vanishing, our conventional notions of quasiparticle transport are no longer valid. While the standard Drude-Sommerfeld theory predicts vanishing conductivity in trivial dispersionless bands, in the dispersionless topological bands the electronic wave functions entangle leading to unconventional (non-Drude) quantum transport. We here research the quantum transport in topological flat bands, and find that the quantum-geometric (entanglement) contribution gives rise to several quantum transport anomalies. We highlight structurally similar expressions for strong anomalies in thermoelectric response and superfluid flow in the flat bands. The thermopower anomaly in topological flat bands is reaching values of the quantum unit of thermopower ($\frac{k_B}{e}ln2\approx 60\mu \mathrm{V}$/k)—the behavior commensurate with the thermopower anomalies in twisted bilayer graphene at the magic angle [Nat. Phys. 18, 290 (2022)].

Close

PrevNext

View figure in article

• Flat bands
• Hall effect
• Multiband superconductivity
• Quantum transport
• Superfluid density
• Topological materials