From electron pairs to fractions in van der Waals heterostructures

by Daniele Guerci (MIT)

Wednesday 7 Jan 2026, 11:00 → 12:00 Europe/Zurich

WHGA/121

Superconductivity and the fractional quantum Hall effect have long been viewed as mutually exclusive, since the strong magnetic fields required for fractionalization typically suppress superconductivity. Recent observations of time-reversal-breaking, spin- or valley-polarized superconductivity coexisting with fractional quantum anomalous Hall states—most notably in rhombohedral graphene and twisted MoTe₂ [1,2]—challenge this paradigm.

 

In this seminar, I will present recent theoretical advances [3] that establish a unified framework linking superconductivity and fractionalization, thereby shedding new light on their interplay in flat Chern bands. I will argue that the emergence of superconductivity is fundamentally tied to the breaking of Galilean invariance, originating from the inhomogeneous emergent magnetic fields synthetized in van der Waals heterostructures. This mechanism opens qualitatively new routes to unconventional superconductivity at the interface of quantum Hall physics and strong electronic correlations.

 

[1] T. Han, Z. Lu et al., Signatures of chiral superconductivity in rhombohedral graphene, Nature,  643, 654 (2025)

[2] Fan Xu, Zheng Sun, et al., Signatures of unconventional superconductivity near reentrant and fractional quantum anomalous Hall insulators, arXiv:2504.06972 (2025)

[3] D. Guerci, A. Abouelkomsan, L. Fu, From Fractionalization to Chiral Topological Superconductivity in Flat Chern Band, Physical Review Letter 135, 186601 (2025) [Editors’ Suggestion]