Switching Graphitic Polytypes in Elastically Coupled Islands

TL;DR

This paper demonstrates controllable switching between different graphitic polytypes in nanoscale islands using minimal shear force, revealing potential for multiferroic and SlideTronic applications.

Contribution

It introduces super-lubricant arrays of polytypes (SLAP) devices with shear-induced polytype switching in graphene islands, enabling deterministic control of stacking configurations.

Findings

Switching occurs under shear force as low as 6 nN.

Long-range elastic relaxations facilitate stacking dislocation nucleation.

Confined boundary strips enable robust, deterministic polytype switching.

Abstract

Van der Waals polytypes are commensurate configurations of two-dimensional layers with discrete crystalline symmetries and distinct stacking-dependent properties. In graphitic polytypes, the different stacking arrangements of graphene sheets exhibit rich electronic phases, such as intrinsic electric polarizations, orbital magnetizations, superconductivity, and anomalous fractional Hall states. Switching between these metastable periodic configurations by controlling interlayer shifts unlocks intriguing multiferroic responses. Here, we report super-lubricant arrays of polytypes (SLAP) devices, with nanometer-scale islands of Bernal polytypes that switch into Rhombohedral crystals and vice versa under a shear force as low as 6 nano-Newtons. We assemble these four-layer SLAP structures by aligning a pair of graphene bilayers above and under circular cavities in a misaligned spacer layer. Using local current measurements, we detect the shifts between the active bilayers and reveal long-range elastic relaxations outside the cavities that enable efficient nucleation and spontaneous sliding of stacking dislocation inside the islands. We demonstrate configurable, deterministic, and robust polytype switching by confining these boundary strips in narrow cavity channels that connect the islands. Such controlled switching between elastically-coupled single-crystalline islands is appealing for novel multiferroic SlideTronic applications.