Quantum Wigner molecules in moir\'{e} materials

Abstract

The few-body problem (with $N \leq 6$ fermionic charge carriers) in isolated moir\'{e} quantum dots (MQDs) in transition metal dichalcogenide (TMD) bilayer materials with integer fillings, $\nu \geq 2$, is investigated by employing large-scale full configuration interaction (FCI, also termed exact-diagonalization) computations, and by performing a comparative analysis of the ensuing first-order (charge densities, CDs) and second-order (conditional probability distributions, CPDs) correlation functions. With parameters representative of bilayer experimental TMD setups, our investigations reveal the determining role of the strong inter-particle Coulombic repulsion in bringing about Wigner molecularization, which is associated with many-body physics beyond both that described by the Aufbau principle of natural atoms, as well as by the widely used Hubbard model for strongly-interacting condensed-matter systems. In particular, for weak and moderate trilobal crystal-field deformations of the MQDs, the imperative employment of the CPDs brings to light the geometrical polygonal-ring configurations underlying the Wigner molecules (WMs) that remain hidden at the level of a charge-density analysis, apart from the case of $N=3$ when a pinned WM emerges in the charge density due to the coincidence of the $C_3$ symmetries associated with both the intrinsic geometry of the $N=3$ WM and the TMD trilobal crystal-field of the confining pocket potential. The FCI numerically exact-diagonalization results provide critical benchmarks for assessing and guiding the development of future computational methodologies of interacting strongly-correlated fermions in isolated MQDs and their superlattices in TMD materials.