Portrait of locally driven quantum phase transition cascades in a molecular monolayer

TL;DR

This study demonstrates a locally controlled quantum phase transition cascade in a 2D molecular monolayer, revealing detailed interactions and paving the way for engineered quantum correlations in patterned structures.

Contribution

It introduces a method to tune quantum phase transitions at the single-molecule level using a movable electrostatic gate in a 2D supramolecular network.

Findings

Sequential change from Kondo-screened to paramagnetic phase at individual molecules

Reconstruction of complex electron interactions in the lattice

Potential for engineering quantum correlations in designed patterns

Abstract

Strongly interacting electrons in layered materials give rise to a plethora of emergent phenomena, such as unconventional superconductivity. heavy fermions, and spin textures with non-trivial topology. Similar effects can also be observed in bulk materials, but the advantage of two dimensional (2D) systems is the combination of local accessibility by microscopic techniques and tuneability. In stacks of 2D materials, for example, the twist angle can be employed to tune their properties. However, while material choice and twist angle are global parameters, the full complexity and potential of such correlated 2D electronic lattices will only reveal itself when tuning their parameters becomes possible on the level of individual lattice sites. Here, we discover a lattice of strongly correlated electrons in a perfectly ordered 2D supramolecular network by driving this system through a cascade of quantum phase transitions using a movable atomically sharp electrostatic gate. As the gate field is increased, the molecular building blocks change from a Kondo-screened to a paramagnetic phase one-by-one, enabling us to reconstruct their complex interactions in detail. We anticipate that the supramolecular nature of the system will in future allow to engineer quantum correlations in arbitrary patterned structures.