New topological phase discovery could lead to significant advances in nanotechnology. Using a new platform for topological physics research in nanoscale devices, Cambridge researchers have detected a new topological phase in a two-dimensional system.
A wide variety of phenomena in physics and materials science have been investigated experimentally and theoretically using two-dimensional materials such as graphene. Beyond graphene, there are several 2D materials with various physical properties. This is encouraging for possible applications in nanotechnology, where various functionalities can be added to devices by combining various 2D materials or layer stacks.
What is the Importance of Ferroelectricity?
It has recently been shown that ferroelectricity develops when one layer slides on top of another and breaks the symmetry in materials such as hexagonal boron nitride (hBN), which are less symmetrical than graphene. A useful property for information processing and memory storage, ferroelectricity is the replacement of a material's electric dipole moment with an electric field.
Moiré superlattice is an excellent interference pattern that occurs when two-dimensional materials are bent relative to each other; this pattern can significantly change the physical properties of materials. The bending of HBN and related materials causes the various stacking regions to become polarized, resulting in a regular polar field network and ferroelectricity, which has been shown.
What are Meron and Antimeron?
In this new study, published in Nature Communications, scientists from the University of Liège in Belgium and the Cambridge Cavendish Laboratory have discovered that there is more to these polar areas than previously known. These are topological in nature and form objects called meron and antimeron.
The first author, who started this experiment at the Cavendish Laboratory and is now at Harvard University in the USA, is Dr. Daniel Bennett stated that the polarization in twisted systems is in the out-of-plane direction, that is, in the direction perpendicular to the layers.
We discovered that symmetry breaking induced by shear or bending also produces an in-plane polarization of comparable strength to out-of-plane polarization. The symmetry of the layers completely determines the shape of the cute vector field created by the in-plane polarization.
The in-plane polarization finding shows that the electrical properties of 2D spun systems are much more complex than previously thought. More importantly, the scientists discovered that the polarization in these twisted bilayers is topologically non-trivial by combining both the in-plane and out-of-plane components of polarization.
Working on this study with his team at the Cavendish Laboratory, Dr. According to Robert-Jan Slager, “In each field, the polarization field rotates half a turn, forming a topological object known as a meron (half skyrmion).” A strong network of meron and antimeron develops across the twisted layer.
According to Bennett, most objects in physics can be explained in terms of energy. Nature is inefficient and prefers to complete tasks as quickly as possible, reducing a system's energy requirements in the process.
A material usually chooses the phase with the lowest energy as its new phase. Topological phases and properties, on the other hand, are governed by multiple symmetries of a system rather than energy. Physical properties of a system, such as electric or magnetic fields, can develop complex patterns that become entangled or knotted because they require symmetry.
According to Slager, untying these knots requires a lot of energy, making these structures quite durable. For example, in the field of topological quantum computing, the ability to make, destroy, and manipulate these topological objects is particularly attractive.
To achieve this, the researchers plan to advance their understanding of topological polarization and create a proof-of-concept device that will allow them to organize or generate new and intriguing physical phenomena using the polar merons/antimerones they have discovered.
Source: phys.org/news
Günceleme: 30/03/2023 10:45