Switching between Mott-Hubbard and Hund physics in moiré quantum simulators

Abstract

Mott-Hubbard and Hund electron correlations have been realized thus far in separate classes of materials. Here, we show that a single moiré homobilayer encompasses both kinds of physics in a controllable manner. We develop a microscopic multiband model that we solve by dynamical mean-field theory to nonperturbatively address the local many-body correlations. We demonstrate how tuning with twist angle, dielectric screening, and hole density allows us to switch between Mott-Hubbard and Hund correlated states in a twisted WSe${}_2$ bilayer. The underlying mechanism is based on controlling Coulomb-interaction-driven orbital polarization and the energetics of concomitant local singlet and triplet spin configurations. From a comparison to recent experimental transport data, we find signatures of a filling-controlled transition from a triplet charge-transfer insulator to a Hund-Mott metal. Our finding establishes twisted transition metal dichalcogenides as a tunable platform for exotic phases of quantum matter emerging from large local spin moments.

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• Quenched pair breaking by interlayer correlations as a key to superconductivity in La${}_3$Ni${}_2$O${}_7$
• Mixed singlet-triplet superconducting state within the moiré $t$-$J$-$U$ model as applied to the description of twisted WSe${}_2$ bilayer
• divERGe implements various Exact Renormalization Group examples
• Theory of intervalley-coherent AFM order and topological superconductivity in tWSe${}_2$
• Pressure-tuned many-body phases through $\Gamma$-K valleytronics in moiré bilayer WSe${}_2$
• Frozen spin ratio and the detection of Hund correlations
• Site-polarized Mott phases competing with a correlated metal in twisted WSe${}_2$
• Chern-Selective multi-valley Flat Bands in Twisted Mono-Bilayer and Mono-Trilayer MoTe${}_2$