Flat electronic bands from cooperative moir\'e and charge order

TL;DR

This paper demonstrates how charge-density waves can induce emergent moiré periodicity in heterostructures, leading to flat electronic bands and tunable correlated phases, with potential for engineering novel moiré materials.

Contribution

It reveals a new mechanism where charge order creates emergent moiré patterns, enabling control over flat bands in heterostructures beyond fixed lattice mismatch effects.

Findings

Charge-density waves induce emergent moiré periodicity.

Emergent moiré leads to strong band flattening.

Band flattening can be switched off by doping.

Abstract

The formation of flat electronic bands from long-wavelength superperiodic moir\'e potentials in van der Waals heterostructures underpins the creation and control of a host of highly-tuneable correlated and topological phases. The underlying moir\'e periodicity is, however, typically considered a fixed property of the heterostructure. Here, we show how the development of a charge-density wave (CDW) in one of the constituent materials can create an emergent moir\'e periodicity, realising a superperiodic potential in TiSe$_2$/graphite epitaxial heterostructures with an order-of-magnitude longer wavelength than that expected from the normal-state lattice mismatch. We demonstrate how this drives the formation of a remarkably strong band flattening, which can be readily deactivated by carrier doping across the CDW phase transition, opening new prospects for engineering moir\'e matter by exploiting the rich many-body states of the parent compounds of 2D heterostructures.