Light-induced irreversible structural phase transition in trilayer graphene

Abstract

A crystal structure has a profound influence on the physical properties of the corresponding material. By synthesizing crystals with particular symmetries, one can strongly tune their properties, even for the same chemical configuration (compare graphite and diamond, for instance). Even more interesting opportunities arise when the structural phases of crystals can be changed dynamically through external stimulations. Such abilities, though rare, lead to a number of exciting phenomena, such as phase-change memory effects. In the case of trilayer graphene, there are two common stacking configurations (ABA and ABC) that have distinct electronic band structures and exhibit very different behaviors. Domain walls exist in the trilayer graphene with both stacking orders, showing fascinating new physics such as the quantum valley Hall effect. Extensive efforts have been dedicated to the phase engineering of trilayer graphene. However, the manipulation of domain walls to achieve precise control of local structures and properties remains a considerable challenge. Here, we experimentally demonstrate that we can switch from one structural phase to another by laser irradiation, creating domains of different shapes in trilayer graphene. The ability to control the position and orientation of the domain walls leads to fine control of the local structural phases and properties of graphene, offering a simple but effective approach to create artificial two-dimensional materials with designed atomic structures and electronic and optical properties.

Experimental observation of ABCB stacked tetralayer graphene

“…The ABCB domains were stable over the course of several weeks at ambient conditions as well as when subjected to s-SNOM and Raman measurements at moderate laser powers. At higher laser power, we observed the shrinkage of domains (for details see SI S1) which has also been observed for metastable rhombohedral TLG [13].…”

“…The most common stacking in FLG is Bernal stacking, which is the energetically favorable configuration [12], while rhombohedral stacking is less common [13,14]. For tetralayer graphene (4LG), besides rhombohedral and Bernal (ABAB) stackings, also a mixed stacking has been predicted to be metastable, namely the equivalent stackings ABCB and ABAC (here denoted as ABCB) [12,15], c.f.…”

Large change of interlayer vibrational coupling with stacking in Mo$_{1-x}$W$_{x}$Te$_{2}$

“…The possible connection between the band structure and interlayer vibrational coupling may yield insight into how the transitions in Mo 1−x W x Te 2 are effected by optical or electronic means; such means include pulses of light in ultrafast spectroscopy [30], an electron beam [41], and an applied electric field (for few-layer WTe 2 ) [18,40]. Additionally, there are other materials that exhibit stacking transitions in few-layer films even when not seen in the bulk; such transitions can be induced with an applied electric field on bilayer hexagonal boron nitride [48], and with laser irradiation on trilayer graphene [49]. Given the difficulty of calculating properties that depend on the weak interlayer interactions, our finding that the interlayer vibrational coupling can change by ∼20% between differently-stacked phases should provide insight into how stacking transitions may occur in a wide range of other systems.…”

Light‐Induced Quantum Anomalous Hall Effect on the 2D Surfaces of 3D Topological Insulators

“…There are already several theoretical proposals and experimental observations that light (or focused laser pulses) can trigger structural phase transitions in both 3D bulk materials and low-dimensional nanostructures. [1][2][3] In addition, light can also change the electronic structure and induce electronic phase transitions. In insulators or semiconductors, above-bandgap light can excite electron-hole pairs, and the system would acquire metallic properties in e.g., carrier transports.…”