Crystallizing electrons with artificially patterned lattices

TL;DR

This paper introduces a lithographic method to create tunable Wigner crystal states in graphene-MoSe2 heterostructures, achieving higher temperature stability and real-time control over electron crystallization.

Contribution

The authors develop a nanofabrication technique to pattern a triangular lattice directly into graphene, enabling reconfigurable and more thermally stable Wigner crystals in monolayer MoSe2.

Findings

Wigner crystals observed up to 15 K and high electron densities

Real-time switching between crystalline and unstable states demonstrated

Order of magnitude improvement in stability over pristine MoSe2

Abstract

Wigner crystals are typically confined to ultralow temperatures where thermal motion is frozen out. Moir\'e superlattices in twisted two-dimensional materials have extended their stability to higher temperatures and densities, but rely on delicate stacking that fixes the lattice geometry and limits tunability. Here we demonstrate a lithographic approach that bypasses these constraints. Using high-resolution nanofabrication, we pattern a nanoscale triangular lattice directly into a graphene gate integrated with a monolayer MoSe2 semiconductor. This engineered potential landscape localizes electrons into generalized Wigner crystal states that persist up to 15 K and densities of 2X10^12 cm-2, representing an order of magnitude improvement over pristine monolayer MoSe2. Gate-voltage control allows real-time switching between stable and unstable crystalline states, with the latter exhibiting stochastic telegraph noise from nearly degenerate configurations. This work demonstrates the ability of this platform to transform Wigner crystals from fragile, static phases into reconfigurable quantum matter.