Regensburg 2025 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 19: Focus Session: Strongly Correlated Quantum States in Moire Heterostructures (joint session TT/HL/MA)
HL 19.5: Topical Talk
Tuesday, March 18, 2025, 11:45–12:15, H36
Gate-Tunable Bose-Fermi Mixture in a Strongly Correlated Moiré Bilayer Electron System — •Nathan Wilson1, Amine Ben Mhenni1, Wilhelm Kadow2, Mikołaj Metelski1, Adrian Paulus1, Alain Dijkstra1, Jonathan Finley1, and Michael Knap2 — 1Walter Schottky Institute, TU Munich, Garching, Germany — 2School of Natural Sciences, TU Munich, Garching, Germany
Quantum gases consisting of species with distinct quantum statistics, such as Bose-Fermi mixtures, can behave in a fundamentally different way than their unmixed constituents. This makes them an essential platform for studying emergent quantum many-body phenomena such as mediated interactions and unconventional pairing. Here, we realize an equilibrium Bose-Fermi mixture in a bilayer electron system implemented in a WS2/WSe2 moiré heterobilayer with strong Coulomb coupling to a nearby moiré -free WSe2 monolayer. Absent the fermionic component, the underlying bosonic phase manifests as a dipolar excitonic insulator. By injecting excess charges, we show that the bosonic phase forms a stable mixture with added electrons but abruptly collapses upon hole doping. We develop a microscopic model to explain the unusual asymmetric stability with respect to electron/hole doping. By monitoring excitonic resonances from both layers, we demonstrate stability of the phase over a wide range in the boson/fermion density phase space, in agreement with theoretical calculations. Our results further the understanding of phases stabilized in moiré bilayer electron systems and demonstrate their potential for exploring the exotic properties of equilibrium Bose-Fermi mixtures.
Keywords: 2D materials; Strongly correlated electrons; Moiré materials