Tailoring the band structure of twisted double bilayer graphene with pressure

TL;DR

This paper demonstrates that applying hydrostatic pressure to twisted double bilayer graphene allows precise tuning of its band structure, including flat bands and topological gaps, enhancing control for strongly correlated physics applications.

Contribution

It introduces pressure as a new tuning parameter for band structure engineering in twisted double bilayer graphene, complementing gating techniques.

Findings

Pressure up to 2 GPa significantly alters flat bands and band gaps.

Hydrostatic pressure induces a topologically non-trivial band gap at charge neutrality.

Experimental results agree well with theoretical simulations.

Abstract

Twisted two-dimensional structures open new possibilities in band structure engineering. At magic twist angles, flat bands emerge, which give a new drive to the field of strongly correlated physics. In twisted double bilayer graphene dual gating allows changing the Fermi level and hence the electron density and also allows tuning the interlayer potential, giving further control over band gaps. Here, we demonstrate that by applying hydrostatic pressure, an additional control of the band structure becomes possible due to the change of tunnel couplings between the layers. We find that the flat bands and the gaps separating them can be drastically changed by pressures up to 2 GPa, in good agreement with our theoretical simulations. Furthermore, our measurements suggest that in finite magnetic field due to pressure a topologically non-trivial band gap opens at the charge neutrality point at zero displacement field.