SKM 2023 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

TT: Fachverband Tiefe Temperaturen

TT 61: Focus Session: Correlations in Moiré Quantum Matter II

TT 61.4: Vortrag

Donnerstag, 30. März 2023, 18:30–18:45, HSZ 201

Nontrivial quantum geometry of multiband systems and implications for flat bands — •Johannes Mitscherling — Department of Physics, University of California, Berkeley, California 94720, USA

Studying the geometry of wave function manifolds helps us to identify and understand phenomena whose descriptions are not captured by the sole knowledge of the energy dispersion. A prominent example of recent interest is the distance between wave functions captured by the quantum metric. Flat-band systems are promising candidates for novel fascinating quantum metric effects since well-known contributions to observables that depend on the slope or curvature of the dispersion vanish. For instance, the dominant contribution to the superfluid stiffness and the dc electrical conductivity is proportional to the integrated quantum metric for flat bands. In this talk, I will address the role of band degeneracy in these quantum metric effects. I will use the developed framework for dc electrical conductivity [PRB 105, 085154 (2022), PRB 106, 165133 (2022)] to contrast nondegenerate and degenerate band manifolds. We will explore the common mathematical description in terms of Grassmannian manifolds and its concrete implications, such as lower bounds and the nonadditivity of the quantum metric. I close by illustrating how these concepts can be directly extended to other observables.

J.M. acknowledges support by the German National Academy of Sciences Leopoldina through grant LPDS 2022-06.