48 research outputs found
Promoting College Student Development through Collaborative Learning: A Case Study of Hevruta
Multi-layered atomic relaxation in van der Waals heterostructures
When two-dimensional van der Waals materials are stacked to build
heterostructures, moir\'e patterns emerge from twisted interfaces or from
mismatch in lattice constant of individual layers. Relaxation of the atomic
positions is a direct, generic consequence of the moir\'e pattern, with many
implications for the physical properties. Moir\'e driven atomic relaxation may
be naively thought to be restricted to the interfacial layers and thus
irrelevant for multi-layered heterostructures. However, we provide experimental
evidence for the importance of the three dimensional nature of the relaxation
in two types of van der Waals heterostructures: First, in multi-layer graphene
twisted on graphite at small twist angles () we
observe propagation of relaxation domains even beyond 18 graphene layers.
Second, we show how for multi-layer PdTe on BiSe the moir\'e
lattice constant depends on the number of PdTe layers. Motivated by the
experimental findings, we developed a continuum approach to model multi-layered
relaxation processes based on the generalized stacking fault energy functional
given by ab-initio simulations. Leveraging the continuum property of the
approach enables us to access large scale regimes and achieve agreement with
our experimental data for both systems. Furthermore it is well known that the
electronic structure of graphene sensitively depends on local lattice
deformations. Therefore we study the impact of multi-layered relaxation on the
local density of states of the twisted graphitic system. We identify measurable
implications for the system, experimentally accessible by scanning tunneling
microscopy. Our multi-layered relaxation approach is not restricted to the
discussed systems, and can be used to uncover the impact of an interfacial
defect on various layered systems of interest.Comment: 17 pages, 7 figure