[Paper Review] Atypical sliding and Moire ferroelectricity in pure multilayer graphene

Liu Yang, Shi-Ping Ding+2 more|PubMed|May 12, 2023

Graphene research and applications8 citations

TL;DR

The paper presents first-principles evidence that multilayer graphene with more than three layers can be ferroelectric via interlayer sliding, with polar states arising from across-layer stacking symmetry breaking and unconventional Moire ferroelectric patterns.

ABSTRACT

Most nonferroelectric two-dimensional materials can be endowed with so-called sliding ferroelectricity via nonequivalent homobilayer stacking, which is not applicable to monoelement systems like pure graphene bilayer with inversion symmetry at any sliding vector. Herein, we show first-principles evidence that multilayer graphene with N>3 can all be ferroelectric, where the polarizations of polar states stem from the symmetry breaking in stacking configurations of across layer instead of adjacent layer, which are electrically switchable via interlayer sliding. The nonpolar states can also be electrically driven to polar states via sliding, and more diverse states with distinct polarizations will emerge in more layers. In contrast to the ferroelectric moiré domains with opposite polarization directions in twisted bilayers reported previously, the moiré pattern in some multilayer graphene systems (e.g., twisted monolayer-trilayer graphene) possess nonzero net polarizations with domains of the same direction separated by nonpolar regions, which can be electrically reversed upon interlayer sliding. The distinct moiré bands of two polar states should facilitate electrical detection of such sliding moiré ferroelectricity during switching.

Motivation & Objective

• Motivate the search for ferroelectricity in pure multilayer graphene beyond bilayers.
• Show that polar states arise from across-layer stacking symmetry breaking, not adjacent-layer symmetry.
• Demonstrate electrical switchability of polar states via interlayer sliding.
• Highlight that non-polar states can be driven to polar states by sliding and are nearly degenerate in energy.
• Explore how increasing layer number N>3 expands possible polar configurations.

Proposed method

• Perform first-principles calculations to study stacking configurations and their polarizations in multilayer graphene.
• Identify polar states arising from across-layer stacking symmetry breaking.
• Evaluate interlayer sliding as a mechanism to electrically switch between polar and non-polar states.
• Compare Moire patterns and net polarization in twisted multilayer graphene systems.
• Characterize how distinct Moire bands correlate with polar state switching and electrical detectability.

Experimental results

Research questions

• RQ1 Can pure multilayer graphene with N>3 exhibit ferroelectricity despite inversion symmetry in certain configurations?
• RQ2 Are polar states stabilized by across-layer stacking symmetry breaking and switchable by interlayer sliding?
• RQ3 Do Moire patterns in twisted multilayer graphene produce net polarization that can be electrically controlled?
• RQ4 How does increasing layer number N affect the diversity of polar configurations and their energies?

Key findings

• Multilayer graphene with N>3 can be ferroelectric according to first-principles evidence.
• Polar states originate from symmetry breaking across layers, not just adjacent layers.
• Non-polar states can be driven to polar states by interlayer sliding and are nearly degenerate in energy.
• Some Moire patterns (e.g., twisted monolayer-trilayer graphene) have nonzero net polarization with same-direction domains separated by non-polar regions.
• Distinct Moire bands corresponding to polar states enable electrical detection during switching.